Why can’t the pro-Remain parties unite in a single electoral alliance to defeat Nigel Farage’s Brexit Party on 23 May? That was the complaint dominating the Easter-tide conversations of Britain’s liberal centre.

The simple answer is that, while Farage is constructing a single-use tool to destroy the Tory party and coerce Britain towards a hard Brexit, the rest of us cling to the quaint belief that politics should be about parties, programmes, reasoned debate and giving voters a choice.

Labour, whose entire strategy is to try to win sections of its voting base that wanted to leave the EU back to its progressive politics, cannot profitably turn the 23 May vote into a proxy referendum on Europe.

It can, however, do much more than it is currently inclined to, to advance its strategic goal.

Right now Labour’s front bench is trapped in a situation that was not of its own making. It took part in initial discussions with the government in good faith. But the Tories have offered nothing that could meet Labour’s demand for a customs union; thus there is nothing on offer that could get through parliament.

Nor is it in the gift of Jeremy Corbyn to stop the sudden advance of Nigel Farage’s Brexit Party. It is currently polling above 20 per cent because a section of the electorate, mostly from the right, believes Brexit is such an existential issue that they are prepared to desert the Tories to achieve it, and if necessary destroy the Tory party in the process.

That is a problem for the Tory party, not Corbyn.

What Labour can control is the energy, message and offer it makes to the majority of the British electorate, which is not high on the helium of outrage and xenophobia. Unfortunately, a mixture of classic Labourite routinism, political divisions and bureaucratic manoeuvring have left Labour paralysed as Farage storms ahead in the polls.

Labour insiders report a de-facto freeze on campaigning for the European elections because some fear that a mixed message will blur Labour’s impact in the local council elections on 3 May.

Because Labour never took the European elections seriously, the regional party machine is not well geared to the task. In addition, so long as the party is engaged in talks that might lead to Britain leaving the EU, Labour cannot start campaigning in good faith for the EU elections.

There is also a manifesto issue. Labour, as a member party of the Party of European Socialists (PES), is bound to stand on that group’s manifesto. Corbyn was even at the meeting that agreed it. And its main slogan – Europe for the many not the few – is a straight copy of Corbynism.

The question is: what message is Labour going to attach in its own party manifesto, currently being drafted by Corbyn’s adviser Andrew Fisher, and set for discussion at a 30 April NEC meeting?

It should be obvious that the question of Remain vs Leave is a non-issue for Labour’s manifesto. The entire premise of asking people to vote is that you are going to take your seats. That means fighting on the assumption that Brexit does not happen.

So the first thing Labour should do is leave the government talks. They are going nowhere. It should acknowledge that the electorate is sick of the Brexit crisis, and that many people feel their wishes from the 2016 referendum are being ignored, but lay the blame squarely on the chaotic May administration.

Next it should publish a short, clear statement of what it would do – over and above what the PES manifesto says – to radically transform the EU from the inside. It should pledge to fight to revise the Lisbon Treaty, insist on the removal of competition laws, state aid rules and labour market rules that favour big business at the expense of the poor, and which limit the ability of governments to take sovereign decisions about economic policy.

The issue of treaty renegotiation has become a shibboleth for the PES. Despite all the progressive promises in the PES’s manifesto, there is no mention of a new treaty. But Labour would find plenty of allies: the entire GUE-NGL radical left group wants this, as do some from the right of the incoming parliament and many of the left factions within the PES parties.

Since President Macron has offered to reopen the Lisbon Treaty as a way of preventing the collapse of the entire project, Corbyn should promise to make a new Treaty the primary business of the next five years.

Those arguing that Labour should turn the 23 May vote into a proxy referendum on Brexit, or that there should be an alliance between pro-Remain parties to vote tactically, miss the point. The Lib Dems and Change UK would, if elected, prop up the status quo.

Tellingly, the two MEPs who have defected to Change UK were former Tories who now sit as independent members of the conservative European People’s Party (EPP). The Lib Dems would sit alongside Macron in the ALDE group, Change UK might very well sit alongside Merkel – but Labour’s aim should be to form the radical wing of the PES, building a bridge in the incoming parliament with the 50+ MEPs of the radical left, and any Greens or progressive nationalists who want to take part.

Asking Labour to subsume its critique of the EU into a proxy referendum and stand alongside Umunna, Cable and a few wet Tories would repeat the same mistake as the Labour mainstream made in 2016.

In fact, the more you look at the panic and despondency of the political centre, faced with Farage’s rise, the more it looks like a rerun of summer 2016. Remain lost then because it appeared to defend the status quo. Labour’s campaign, its manifesto, its messaging and energy cannot be anything other than a challenge to the status quo.

But it is vital that, either in the manifesto or in an agreed NEC statement, the party reiterates its commitment to putting any Brexit deal to a second referendum.

This is the position supported by 80 per cent of Labour voters, unanimously passed at conference, supported by almost all the MEP candidates themselves and backed by every affiliated trade union except Unite and the CWU.

It’s obvious why this hasn’t happened so far. Since December a group of unelected party officials, together with backbench MPs and union leaders, has been fighting a rearguard policy on the second referendum. Some because they fear – rightly – the culture war it will provoke in working-class communities; others because they have always been closet Lexiteers.

But the moment of truth is approaching for this group. For months they insisted they would “rather concentrate on an election than a referendum”. Well here is an election – and it makes good electoral strategy to fight it on a platform of reform to Lisbon and the offer of a second referendum.

First, because we are internationalists and the outcome matters. In the next European Parliament, the effective “grand coalition” of the PES and EPP will lose its majority. That’s the conclusion of polling analysis released this week by the European Council on Foreign Relations. So what’s needed is an effective alliance of the left: a Red-Red-Green coalition that will fight for social justice and a green new deal.

The second reason campaigning positively for EU reform and a second referendum concerns self-interest.

Every election is a test of the relationship between a party and its electoral base. In the EU elections, where turnout is traditionally low, Labour could wipe the floor with the other parties if it simply mobilised its core voters. The only way to do that is campaigning on what they believe in, not triangulating with what other people think.

Just as important as getting the second referendum into the offer is for Labour to enthusiastically campaign on a vision for Europe. Even if Labour’s own Brexit variant of single market alignment were achieved, you would still want to know what its vision for a reformed EU was.

Despite their residual influence on Twitter, Lexiteers are a busted flush. If, as they claim, delivering Brexit is the paramount issue of democracy and economic sovereignty, and breaking up the multilateral global system is the desired outcome, then logically they should follow George Galloway and vote for Farage’s party.

Much better, given Lexit is not a possible outcome in this election, would be to simply get out of the way – and allow party activists, the candidates and the majority in the shadow cabinet to fight the actual election in front of us in a way designed to win it.