All political parties were too self-absorbed to see it coming, but Nigel Farage’s 32% European election vote created a new dividing line in British politics – taking us well beyond the leave-remain split that has defined Britain since the referendum and threatens to dominate its politics for the foreseeable future.

In the three years since 2016, when we should have been debating the bigger issue that the referendum raised – what kind of Britain we want to become – our rulers have been obsessed with one very narrow question: not even our future relationship with Europe, but merely the terms of our departure from it.

Any leader of our country should have seen that we had to be clear about the Britain we wanted before we could be clear about the Brexit we negotiated – and it is frustration at that failure that has allowed Farage to move in from the wings.

After last Thursday, what is now at issue is far bigger than Brexit: it is a new battle for Britain. This is a battle against intolerance, prejudice, xenophobia and the manufacture of distrust and disunity.

The new division in British politics is between the patriotic majority – tolerant, fair-minded, outward-looking and pragmatic – against the Faragists, who will follow Farage wherever he goes. The dogmatism and divisiveness of their them-versus-us nationalism has more in common with the Le Pens, the Salvinis and the Orbans, and of course the Trumps and Putins, than with the enduring values of the British people.

For what do we discover when we look behind the now well-honed – and well-funded – image of the ordinary bloke who might buy you a drink in the pub, or, more likely, talk you into buying him one?

A close look at the facts shows Farage is out to hijack British patriotism: to whip up a politics of division and hate; weaponise it by deploying the language of betrayal and treachery; and target, demonise and blame immigrants, Europeans, Muslims and anyone else who can be labelled “outsiders” or “the other”. Thus redefining our country as intolerant, inward-looking and xenophobic.

‘While Farage’s anti-immigrant views are well known, the full extent of his instinctive prejudice is shocking.’ Photograph: Stefan Wermuth/Reuters

At a time when antisemitism and Islamophobia need to be outed, Farage wants to undo the very anti‑discrimination and equality legislation that protects minorities. He would set back gender equality, promising, for example, to end the right to maternity pay. And instead of honouring the Brexit campaign’s promise of £350m a week to the NHS, he would demolish it by means of US-style private insurance.

While his anti-immigrant views are well known, the full extent of his instinctive prejudice is shocking; from feeling “awkward” sitting on a train next to people not speaking English, to demanding local referendums on new Muslim mosques and, in a direct attack on free speech, proposing to ban university courses in European studies.

A recent video featured him and Trump cheerleader Steve Bannon discussing, apparently with no hint of irony, a worldwide campaign against globalisation, to be waged through foreign funding of nativist movements. Their plan is to destroy any institutions with the words “European” and “global” in their name.

But it is only because they and so many others have chosen to forget the massive carnage of two world wars, caused by uncontrolled European nationalism, that they can even contemplate a return to it.

But it is Farage who is setting the terms on which Conservatives will choose the next prime minister. For nowhere is his attempt to commandeer patriotism for his own ideological purposes more clearly exposed than in his challenge to Conservative leadership candidates. There is, he claims, only one “true” Brexit and that is to leave the EU on 31 October even if there is no deal in place by then. And in doing so he has imposed his own arbitrary definition of true patriotism – you betray your country if you do not want to leave by 31 October without a deal.

And so, instead of calling out no deal by 31 October as a catastrophic act of economic self-harm that runs wholly counter to the national interest, it has become a Farage-driven test of patriotism that a panicked Conservative party is obliging their leadership candidates to pass.

It is time to draw a line that must not be crossed and to call on the patriotic majority – which includes millions who voted leave out of understandable economic discontent, and millions, too, who last Thursday voted for Farage – to speak up against this descent into the heart of darkness.

It is time also to say to the next prime minister – indeed, to all candidates for Tory leadership – that their party has a fundamental choice to make between running against the Faragists or, as now, racing to the bottom with them. Of course, the stakes have now become even higher because if the UK cannot find a way of coming together, our union of four nations is at risk of falling apart. I harbour the hope that once the truth is out – about the insularity of a Farage-driven politics and the intolerance that is fundamental to it – a Britain that has traditionally prided itself on its tolerance, its engagement with the world and its internationalism will think again about the isolationism that Brexit entails.

The starting point in healing the wounds of our country is to make people proud of the outward-looking, fair-minded Britain we would like to build and has always represented the best of being British. First – and immediately – all parties need to stop the pretence that no deal is anything other than a bad deal and the prelude to a worse deal. But if we are to restore the trust Farage is undermining, we have to address the very real problems that caused the Brexit vote. We have to deal with the fears surrounding immigration, sovereignty, the state of our towns – and high streets – and Britain’s now rampant poverty and inequality.

For months I have been calling for us to go outside the Westminster bubble and hold region-by-region public hearings to seek out a new country-wide consensus in advance of a final vote by the British people. If we engage honestly with each other we will, I believe, find the British people far more tolerant and fair-minded, and less inward-looking and dogmatic than those who have suborned our patriotism, turned it into petty nationalism, and today dominate our politics with such disastrous results.

• Gordon Brown was UK prime minister from 2007 to 2010