Britain is not a rightwing country. There is no appetite to go on a national war footing with an accompanying recession in order to leave the EU without a deal. No appetite, either, for relishing the resulting decades of distrust and animosity with the rest of our continent.

There remains overwhelming attachment to the idea of the United Kingdom, still substantial attachment to the idea of the European Union and wide distrust of Donald Trump’s US. The great majority do not believe our major institutions – the civil service, the Bank of England, the judicial system – are broken because they will not blindly sign up to a no-deal Brexit.

Yet the country is now governed by the most rightwing administration of modern times, led by a duplicitous rogue who wants the country to rally behind his absurd, fantasist rhetoric and to believe in a glorious future built on division, rupture and schoolboy patriotism. The talk about uniting the country with fake one-nation Tory commitments to education, “left-behind” Britain and health are cloaks for a first-order threat to our civilisation, our values and who we are. Britain is at bottom a fair-minded, tolerant country whose citizens look out for each other. All that is to be submerged and forgotten.

The Tory party has now completed its transmutation into a “respectable” version of Nigel Farage’s Brexit party. To contain the ugly forces unleashed by Brexit, it has had to become the creature of its new master – the unparalleled brutality of the cabinet changes was but a part of that. Only thus is there any prospect of the party winning a general election. It is a coup, British style.

Sacked minister urges Boris Johnson to dial down Brexit rhetoric Read more

In the future, it will not be enough to be a Tory to enjoy the benefits of patronage and accompanying social prestige that the party has always deployed to garner support. You will need to be a Brexit Tory – joining Amber Rudd and Nicky Morgan as ready to ignore what you know to be true and right for the country in order to hold on to some political or cultural bauble. We are witnesses to a rightwing revolution whose final destination is an enforced nihilist libertarianism.

What to do? The best of Britain must mount a united, full-fronted roar in response, protecting our values and advocating a wholly different programme to sustain our integrity and inclusiveness as a country while making common cause with the EU. Yes, our capitalism will need to be reshaped, our political system overhauled and our social contract refashioned. But first and foremost comes EU membership, foundational for the rest.

No united front is possible without the Labour party. Johnson has scorned Jeremy Corbyn as a Remainer. The Labour leader should glory in the epithet, own it and turn it to his advantage – there is now no room for dissimulation and triangulation. In a de facto civil war initiated by the Brexit right, there is no middle ground. We are in a battle for the very idea of a country and the Labour leadership has to reaffirm that it is a national party and will in the national interest reach across party lines. Johnson’s Brexit Tories, and their slavish fifth columnist press, are the new sectarian enemy.

Labour has to make the case for Remain as the base for a wider common programme that it will negotiate with the Liberal Democrats, Greens and even dissident liberal Tories. Nationalist parties in Scotland and Wales should be welcomed to sign up; the promise will be a federal Britain inside the EU. They may refuse, but many of their voters will not.

Play Video 1:10 Johnson: 'I do not want no-deal Brexit ... but we must get rid of backstop' – video

The elements are clear. Britain is European to its marrow – our interests, values, intertwined history, belief in a social contract and even our literature are European. We must make common cause with our neighbours, not exchange being the 28th member of the EU to become a non-voting state of the US. The shared ambition must be to build a generous society, living lives all have reason to value. Current levels of inequality are pernicious because they menace that possibility. There is such a thing as society.

Our economy should be populated by companies that define their purpose one way or another as social betterment, including sustainability. The private and public sectors are interdependent parts of a functioning whole – the vibrancy of both is vital for the good of economy and society. The public sector needs proper resources to discharge its function, especially in terms of education and training, and those who work in it must be properly honoured for what they do. Our leaders should be characterised by duty, integrity and honesty. There is an environmental emergency: every aspect of policy should recognise this truth.

The constitution must be organised as a federal Britain in which economic and political power is as close as possible to local people. We want a diverse truth-seeking media, with strong public service broadcasters. Culture is not some dispensable add-on. Music, art, theatre, TV and film speak to our souls.

No common programme of this type is possible without political generosity. Suspend the vendetta against Blairites. Forget Lib Dem leader Jo Swinson’s voting record when in government. She, in turn, should cease her criticisms of Corbyn. Corbyn himself must decide if he can lead such a common front or stand aside for those who will. Caroline Lucas and the Greens need to be recognised as representing a growing and powerful stream of opinion.

One of the reasons for the rise of the right is the willingness of those on the liberal left to attack each other over second- and third-order differences; small gains while the big prize falls to the Brexit right. Now is the moment for a common programme, a common willingness to work together in parliament to block a no-deal Brexit and negotiate whatever pact possible for the inevitable general election.

Johnson’s ruthlessness in reinventing the Tory party as the party of Brexit has to be countered by the creation of an alternative programme for change – and a credible political architecture to deliver it. It’s the challenge of our lives.

• Will Hutton is an Observer columnist