After another week of unmitigated disasters, it must be obvious to even the most ardent anti-EU voter that Theresa May’s amazingly inept government, as currently constituted, is incapable of securing a satisfactory, coherent Brexit deal for all of Britain.

A vicious internal struggle over Europe that began inside the Conservative party in the era of Ted Heath and Margaret Thatcher is now being fought out in public on the parliamentary, national and international stages, with immensely damaging consequences. The debate is no longer mainly about the EU – it is about the Tories. It is about how gaping Tory divisions, ideological, personal, instinctive and prejudicial, are propelling Britain ever more rapidly towards a national humiliation surpassing the 1956 Suez crisis.

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Britain has a Tory problem and, as the clock ticks, it is growing critical. The irresponsible behaviour of many Conservatives at this fraught juncture in the country’s affairs is nothing less than a national disgrace. How can May and her senior colleagues hope to negotiate an orderly exit from the EU when, leaking and briefing against each other, they cannot agree on handling even the most basic issues? How dare David Davis, the Brexit minister, repeatedly try to mislead parliament and the public with his patronising, faux-cheery accounts of the Brussels negotiations, claiming falsely that useful progress is being made? Such breathtaking disingenuousness echoes last year’s mendacious Leave campaign. It is equally objectionable.

By what twisted reasoning do Liam Fox, Jacob Rees-Mogg and fellow hard-Brexit Tories claim a mandate for foisting their extremist minority views on the majority of voters? Whether or not they backed Brexit 15 months ago, most people rightly fear a 2019 cliff-edge meltdown damaging livelihoods, incomes and their children’s and grand-children’s futures. Fox, minister for trade deals sans trade deals, embarrassed Britain, his hosts and himself during a recent visit to Japan by accusing the EU commission of blackmail. It was an ill-judged jibe that said more about the chaos characterising the government’s ineffectual stance than it did about Brussels.

The widening, tribal schisms within the Tory party are coming into brutal focus as the autumn political season opens. One reason is the government’s undisguisably lamentable negotiating performance to date, dramatised by the contrast between the EU’s cool-headed Michel Barnier and Davis’s bombastic blathering. Another reason, more fundamental, is the growing realisation that on almost all the salient issues, May and her team have either failed to agree a reasonable, common position or adopted an unrealistic stance that, as Barnier says with increasing frequency, is “not going to happen”. On all three of the central issues in the first stage of the negotiations – the Irish border, the divorce bill and citizens’ rights – the talks are going backwards. The degree of disagreement is growing.

Thanks to internal Tory machinations, much time as well as effort has been wasted, not least by May’s general election own goal in June and the distracting leadership rivalries it subsequently encouraged. There is now almost no chance that next month’s EU summit will agree sufficient progress has been made to allow an expansion of the talks. There is, perhaps, a year remaining to renegotiate all aspects of Britain’s 40-year-plus relationship with the EU, before any deal must be sent to the 27 national parliaments, regional assemblies and the European parliament for ratification (and also, hopefully, to Westminster). Completing it would be a daunting challenge for the most skilled operator. But skilled operators are what the Tories lack.

Now, just to make matters worse, along comes the benign-sounding European Research Group; in reality, a gaggle of hard Tory Brexiters determined to stop May making any of the necessary concessions. For most sensible people, for example, including worried banks and business leaders, an extended transitional period after March 2019 makes eminent sense. Not so these Tory last ditchers. They suspect a transition is a way to stay in the EU “by stealth”. They demand impractical conditions, including a strict time limit and guarantees on trade.

As the government’s European Union (withdrawal) bill heads for the first of several votes in parliament tomorrow, May also faces pressure from Tory Remainers who, like Labour, are understandably alarmed by the sweeping powers the bill would grant the executive. Speaking for many moderates, Dominic Grieve, the former attorney general, denounced the bill as an “astonishing monstrosity”. But the response from Downing Street and the whips’ office has been to threaten dire retribution against any Tory rebels. May’s simplistic argument, as ever on Brexit, is you are either for us or against us. Trust me, the prime minister says, in effect: the national interest requires that you blindly support whatever I decide is best. And that goes for voters, too.

May’s divisive, didactic stance goes to the heart of Britain’s Tory problem. The problem is, most voters, Conservative or otherwise, do not entirely trust her. The problem is, last summer’s general election, which May fought on highly personalised lines, delivered an unmistakable vote of no confidence in her leadership. The problem is, May has neither the strength, the cunning nor the charisma to bind her party’s long-suppurating wounds over Europe. She plainly does not have the necessary ability to draw competing factions together in an agreed, attainable Brexit platform and keep them firmly in line when the inevitable compromises arise.

The Tory problem bedevilling all that this hapless, perhaps uniquely incompetent administration attempts to do concerns May herself. Sulkily silent, cowed, barely visible outside Westminster, in denial about the coming Brexit train crash and desperately scheming to keep her job, she is a prisoner in Downing Street. For her, there is no escape except through defenestration, no liberation without humiliation and the sack. The idea that May, like Thatcher, can go on and on “for the long term”, and lead her party into the 2022 election, is as believable as Michel Barnier agreeing to be fingerprinted on his next visit to Dover.

It is time for the Tories, for as long as they cling to power, to stop their infighting, get their act together and start behaving like responsible politicians. It is evident the EU negotiators have overreached in key areas. Some of the figures floated in Brussels in respect of Britain’s divorce bill smack more of punishment than fair accounting. The idea that European court of justice law should override British law in respect of EU citizens resident in a post-Brexit Britain is presumptuous. Just imagine trying that on the Americans! And it is true that Jean-Claude Juncker, the commission president, is a disobliging bureaucrat who demeans his office with his apparent Anglophobia.

But May and Davis must get real. Barnier is clearly right when he says their half-baked ideas about keeping the Northern Ireland border wide open are unworkable. The bald fact is that if Britain precipitously quits the single market and customs union, a hard border with all the negatives that entails is unavoidable. When it comes to a financial settlement, the smart move would be to make an offer and by doing so, indicate a limit on what the UK eventually pays. And on migration, given the hostile reaction to last week’s leaked Home Office draft policy document, even May must surely realise that such an approach is unacceptable in principle and massively self-harming in practice.

For the sake of the UK and its international reputation, the fractured, fractious Tories and their limping leader must finally renounce the lie they have peddled ever since last year’s referendum. Yes, Britain voted to leave the EU. No, it did not vote for the economic penury, falling wages, lower living standards, spiralling sterling devaluation and slacker food safety, health and environmental protections that a full-blown rupture with the single market and customs union would surely bring. It did not vote for unequal trade deals with economic superpowers such as China and the US that, if they happen at all, will be the consequence of a weakened Britain going it alone.

Britain did not vote to trash its proud, centuries-old tradition of welcoming foreigners, to diminish the hard-won protections of workers of all hues and backgrounds, to turn overseas students into suspected criminals or to weaken the civic and human rights of ordinary citizens in a constitutional democracy. It did not vote for a discriminatory migration policy that impoverishes our communities and culture, undercuts our industries, earns the contempt of all Europe and disadvantages our citizens abroad. It did not vote to give the government unprecedented legal powers over our lives with which, as we know from experience, it cannot be trusted.

As MPs prepare to vote tomorrow, they should also remember Britain did not vote for, and does not want, an enfeebled parliament that bows down before Downing Street, puts party before country and fails to stand up for the interests of all the people.