A new realignment of the Left is underway and Proportional Representation and the Basic Income are at the core

In Castlefields arena, Natalie Bennett addresses protesters from many different movements, who came together in opposition to the Conservative government in Manchester last Autumn.

Back in the 1980s and 1990s, Liberal and Liberal Democrat leaders Roy Jenkins, Paddy Ashdown and Charles Kennedy followed a course that sought to 'realign the Left' in Britain. Powered by the dominance of Thatcherite conservatism, it sought to change the approach of the left and ultimately lead to co-operation between progressive parties, in opposition to the Conservatives.

First through Liberal-Labour pacts, of which there is an even longer history, next through the breakaway SDP/Liberal Alliance, and then in the form of New Labour-Liberal Democrat talks and cooperation. And Kennedy's 'Real Alternative' campaign banner, even in opposition to a Labour government, reflected the general cohesion of aims on the Left, if not of methods.

That particular movement on the part of the Lib Dems ended with Nick Clegg's leadership. Clegg took the Liberal Democrats back to a policy of equidistance between the two big parties, Labour and the Conservatives.

However, the fall of the coalition and succession of a Conservative to a majority government seems to have triggered a new phase of realignment. The resignations of Clegg and Miliband led to the election of new party leaders, seen to be of very different stripes from their predecessors.

Tim Farron, the new Lib Dem leader, is a campaigning Northern MP and former Party President who stood aloof from, and in polite opposition to, the coalition. So far his efforts have been concentrated on focussing the Lib Dem fightback on the party's roots - in campaigning locally for community issues and nationally on matters of conscience.

Jeremy Corbyn's election as Labour leader seemed to send shockwaves through British politics. Portrayed by the media as a move back to some Michael Foot and Tony Benn, 80s-esque, hard Left position, Corbyn has faced disquiet and malcontent within the Parliamentary party since taking over with a landslide of party members' votes.

After the last five years, the seemingly inevitable alignment of the Liberal Democrats and Labour was shattered. It would be understandable to think finding new common ground would be difficult or impossible between the party Clegg had taken to the Centre, even Centre-Right, and the party Corbyn has been accused of taking to the hard Left.

Yet a new realignment of the Left is under way and the policies that will define the shift are already emerging in the policy debates of both parties.

Both the Liberal Democrats and Labour now seem to be on the same page, finally, when it comes to proportional representation. Both Shadow Chancellor John McDonnell, from Labour's Left, and Chuka Umunna, from Labour's Right, have expressed support for PR. And both parties are engaged in consultations over their future approach to policy, including the welfare system - debates in which the idea of a universal basic income is playing a prominent role.

Ahead of the EU referendum, Farron has even called for a progressive political alliance on Europe - making internationalism again a core value across progressive parties. That matches, in a limited way, the arguments that Caroline Lucas, the Green MP, has been making since the last election that progressive parties need to start working together.

As for the Green Party, in true Green fashion Natalie Bennett is following Caroline Lucas' lead in standing down as party leader once her term is up later this year. So who will lead the Greens through this new realignment, and how they will handle it on into the 2020 general election, is unknown.

But the challenge ahead of the three leaders of Britain's main progressive parties is clear: to stop the Conservatives winning their way to back-to-back governments. Aligning in support of some core common policies is a start.

The next step is to commit to the kind of cooperation on various campaigns and causes that can foster the good will between parties. That mutual respect will be needed to build a real electoral alliance, that stands together behind a limited set of core ideals in opposition to conservatism.

If Labour is going to compete with the SNP in Scotland, it needs to address its own complicated and confusing politics

Labour have a lot of work to do in Scotland if they are to recover from the landslide defeat that cost Jim Murphy his job. Photograph: Jim Murphy and Eddie Izzard meeting retailers in East Renfrewshire by Scottish Labour (License) (Cropped)

In his speech to the Scottish Labour Party conference, Jeremy Corbyn made clear his intention of facing the SNP head on in Scottish Parliamentary Elections in May (BBC, 2015). Corbyn pulled no punches in the speech, which contained barely veiled criticism of SNP. He referred to Labour as the true democratic socialist party, in both "words and in deeds".

Along with new Scottish Labour leader Kezia Dugdale, the Labour leadership face an undoubtedly uphill task. Even accounting for the 'Corbyn Effect' and 'Corbynmania', the general election in May was only the culmination of years of alienation - during which time the popularity of the SNP soared.

If Corbyn wants to outright defeat the SNP, he has to get to grips with Labour's long term Problems. At the last election, Labour lost support in every direction: they lost their base on the Left and amongst the working class by making those supporters feel abandoned; and they lost amongst their targets on the Right because the Tories convinced voters that their abandonment of the Left was not genuine.

Their unclear, inconsistent, positions - that sought to string the Left along without having to pursue Left policies - only led to alienation.

Ahead of Corbyn and Dugdale is the task of making Labour credible again. But rather than how this is usually interpreted - vis a vis embracing mainstream neoliberalism - the renewed credibility requires consistency: clear beliefs, backed by clear motivations, that support clearly communicated stances and policies.

That means Labour has to be very careful of U-turns and wavering - the choice to delay tax credits cuts rather than to kill them outright (BBC, 2015{2}), or Shadow Chancellor John McDonnell's shifting position on George Osborne's fiscal responsibility charter (Perraudin & Wintour, 2015), both being prime examples.

Along with establishing their own position, they also seem determined - if the thinly veiled criticisms from Corbyn's speech tells us anything - to shake the impression people have of the SNP as a true party of the Left.

There certainly are, undoubtedly, some legitimate criticisms to be made with regards to SNP governance (Macwhirter, 2015). And it isn't a departure from reality to suggest that the SNP could be more comfortably described as a broad tent party of the Centre. But the SNP under Nicola Sturgeon is no flash in the pan protest vote, to be undone by the simple bursting of a bubble.

The SNP used disaffection on the Left with Blair and Brown's long rule of Labour to first establish themselves, through Alex Salmond's Scottish minority administration, as a credible party of government. As Labour's credibility sank, the SNP converted that position into a majority in Scotland in 2011 and then a virtual sweep of Scottish seats at Westminster in 2015 under Nicola Sturgeon.

The position of the SNP has been at least a decade in the making. It is a well organised, with visible support that wields distinctive branding and a clear sense of themselves as the opponents of conservatives. Theirs is a formidable position.

If they're to compete, Labour need consistency, clarity and clear communication. Without addressing the complicated and confusing politics with which they alienated supporters as New Labour, they stand little chance of being seen as a credible alternative to the SNP.

Labour's woes continue as the party splits over welfare cuts - where is their unifying idea?

The Labour Party is in the midst of an identity crisis. Two election defeats seem to have completely sapped the party of self-belief and bold ideas and now the party is divided over the merits of the Tory Chancellor's cuts (Perraudin, 2015).

Labour are struggling to come up with a convincing alternative narrative to the one George Osborne is using to bulldoze his way through the public sector. That struggle is pulling the party apart into distinct factions.

Yet a big internal squabble might actually be, in the end, rejuvenating.

The factions in that fight a pretty familiar. There is the New Labour mainstream - a majority of which seem to be more Brownite than Blairite, following the school of Gordon Brown, Alistair Darling, Ed Balls and Ed Miliband. These are the moderates and modernisers, represented by Andy Burnham and Yvette Cooper in the leadership race.

To the Right of the mainstream modernisers there is a faction that has gone under several names, Blue Labour and One Nation Labour in particular. This is the wing of the party, represented by Liz Kendall in the leadership race, that wants Labour to embrace working class conservatism, along with the Far-Right themes of anti-immigration and clampdowns on welfare.

It is also clear that there is a small but significant number of Labour MPs, at the moment with Jeremy Corbyn as their ringleader, who are significantly to the Left of the Labour mainstream. They have stood here against welfare cuts here and Corbyn's leadership campaign has firmly embraced the broader anti-austerity movement.

How this division is healed will depend upon a lot of factors, internal and external to the party. But it is a state of affairs that must ultimately be settled. Labour's determination to be a big tent has largely suppressed or alienated voters on the Left, driving many of them away - particularly in Scotland.

If the moderate or Right-wing faction wins out, how much longer will its Left-wing remain bottled? If the Left-wing wins out, will the mainstream fall in line?

In the face of these issues, there are predictions that Labour faces an extended stay in the wilderness (Moss, 2015). One of the few ways back would encompass a major change of direction: embracing the proposed progressive pact in England and embracing electoral reform that can ensure representative government, showing that Labour is finally working to work co-operatively with others on the Left.

Yet for many progressives, who would have been taking hope from Caroline Lucas' progressive alliance proposal (Lucas, 2015), there will have been an ironically collective sigh of despair when Labour's tendency to give in to populism struck again - this time in the form of Harriet Harman (Wintour, 2015):

"We cannot simply say to the public: you were wrong..."

Why not? What exactly is the point of an opposition party, many on the Left will be asking, is if it isn't going to oppose?

If the party are just going to argue for the same policies as the Tories, differing only on who is better equipped to administer them, then are Labour and the Conservatives anything more than two squabbling factions of essentially the same party?

And if the party is just going to be a reflection of popular opinion, then does it even stand for anything? Where is the belief, the ideology, the theory?

That only produces an image of a Labour Party more interested in power than standing for something. It wants to build trust through sycophancy, not through ideas, theory, facts and reason.

While in the US, Bernie Sanders is proposing a push of support for trade unions, worker-owned co-operatives and the living wage (O'Hara, 2015), Labour are getting themselves in a political twist over whether or not to support Conservative cuts to welfare set to have a disastrous effect on the poorest (White, 2015).

Labour's next leader has to find a way to navigate these splits, these contradictions and the party's overall idealistic emptiness (Hawkins, 2015). There are internal rifts to heal and the Centre-Left of the political spectrum filled with alternatives to navigate. The leadership race itself, with its warts and all exposure of the party's factions is a helpful start in the process of reconciliation.

For the external matters, co-operation is surely Labour and the Left's best hope of opposing the Conservatives on big progressive issues like human rights and electoral reform. For the party's internal struggle, the answer can only be found by digging deep. By looking for the roots of what unites Labour supporters of all stripes and all those allied to the socialist and democratic movement.

To, humbly, get the ball rolling, here one word that offers a place to start: Justice.

Liberals have liberty. Greens have sustainability. With these words, and the ideas they represent, they can construct coherent tests for any policy. Labour seem to lost their connection to a simple and fundamental idea that would underwrite social democratic and democratic socialist analysis, and so their ability to construct a meaningful and consistent narrative.

The new leader of the Labour Party, to be announced in September, has to reclaim a unifying idea - like Justice - if they are to lead the party back out of the fractious wilderness.