What galaxy are you in? That’s the real question posed by this election and one our political system is not designed to answer.

After a disastrous dinner at Downing Street last week, Jean-Claude Juncker briefed Angela Merkel that Theresa May was in a “different galaxy” to those negotiating on behalf of the EU27.

May expects Britain to leave Europe while paying nothing; she expects her threat to walk away without an agreement to achieve a trade deal as good as single-market membership; she expects the talks to remain secret. Juncker gently explained that all these expectations were illusory. He warned that the British prime minister was “deluding herself” and that there is now more than a 50% chance that Britain will crash out of Europe without a deal in place.

As we face the coming election, then, whose galaxy do you want to be in? What we are up against is not just the antics of the Tory negotiating team – May, Boris Johnson and David Davis – but also a galaxy of pub bores, Rotarians and golf-club sexists. A galaxy populated by those who worry about the hijab, halal meat and obsess about the St George Cross. A galaxy in which the concept of universal human rights is alien. A galaxy where it is fashionable to sneer at those who queue for free food – but to laud those who queued for free money in the the privatisation giveaways of the Thatcher years.

Constructing a civil government with such people is, for the progressive majority of Britain, always a challenge. But if May gets her way over Brexit, it will be impossible.

The election has become a power-grab by the racist pub bores of Britain. And this is how we can stop it. First, to recognise that the issue of competence and coherence in the anti-Tory camp matters. May’s “strong and stable” mantra is designed to expose the crucial weakness of the progressive negotiating position on Brexit, which arises – as I have repeatedly warned in this column – from the collapse of Labour’s support in Scotland.

Even before Brexit, English voters swung away from Labour when it seemed the party might be prepared to govern in coalition with the SNP. Labour’s official response – to refuse such a coalition and challenge the SNP to prop up a minority Labour government – makes sense. But, in the context of Brexit, it is not enough.

If there is to be a government that is not Conservative, voters want to know what that government’s negotiating position on Brexit would be.

Labour’s position is, at last, fairly clear. It would not walk away without a deal, says Keir Starmer; that means it would negotiate beyond the artificial deadline of 2019, if necessary. It will not leave without “retaining the benefits of the single market and the customs union”.

Starmer leaves open the option of staying in the single market but says the organisational outcome is “secondary”. This is a mistake. The first request to Europe should be a clear and bold one: to stay in the EEA on special terms while suspending freedom of movement for some categories of worker.

But an even bigger mistake is being made in Holyrood. As is now clear, tying Brexit and the second indyref together has been a tactical disaster for first minister Nicola Sturgeon. She let May pull the wool over her eyes with hints of a “differential approach for Scotland” which have since been shelved. Now she has to fight off a surge of unionist voters swinging to the Tories.

Sturgeon knows that a Tory landslide in England, if backed by seven or eight Scottish Tory MPs, would finish off Scotland’s hopes of independence. But she is so locked in to fighting Labour that she cannot seem to stop and consider the consequences.

The leaderships of both the SNP and Labour should commit to seeking single-market access, customs union membership and membership of the European Free Trade Association (Efta). They should overtly align their Brexit offers now – before the election – and pull the realists among the Liberal Democrats into the project if possible. All the opposition parties could sign up, today, to a joint approach to EU migrants in Britain and British citizens in the EU27.

If the parties of progressive Britain cannot bring themselves to present a common Brexit offer, we the citizens should do it from below. Such work will not be wasted, even if May manages to win in June – because the Juncker leak confirms her Brexit strategy will not succeed.

Tory-led Britain, within two years, will be on its knees begging the commission for time and goodwill as the truck queues build at Dover and Strabane. That’s what every knowledgable observer understands from the Juncker leak.

It is not an illusion for Labour and SNP activists to believe they can defeat the Tories on the social and economic arguments alone. But if they begin to, and the polls narrow, the “coalition of chaos” mantra will eclipse the “strong and stable” one. Meanwhile, inhabitants of the rightwing nationalist galaxy are creating their own coalition of cruelty around May’s Brexit plan. That is the meaning of Ukip’s polling slump: its voters are switching to the Tories. Whether you’re Labour, Green, Lib Dem or nationalist, you will face a Tory-Ukip alliance in all but name in key constituencies.

The appalling myopia on display during May’s disaster-dinner with Juncker should be a call to action – if necessary from below, and in defiance of party bureaucracies. And if we can’t have a progressive alliance, we can at least have a people’s Brexit plan, and it only has to involve four points:

• EU citizens can remain here unconditionally.

• Single-market membership or its equivalent is sought, and not ruled out before the talks begin. Single-market access, matching today’s benefits, is a red line.

• We rule out leaving Europe without a deal.

• We pay the EU some of the billions it demands now, to buy time and goodwill.