I don’t mean to display the smallest trace of sympathy when I say that the people who brought us Brexit hid their secrets from themselves as much as others. They are as guilty of failing to face their own motives and contradictions as of deceiving the country. Their failure to be honest has produced the gravest political crisis since the Second World War. It has spread from the tight group around the TaxPayers’ Alliance and Vote Leave campaign to infect both left and right, which, even at this late stage, cannot level with the electorate.

Allow me to start at the bottom with the little creatures who scurry around British conservatism’s fake grassroots, for that is where it began. The very name “the TaxPayers’ Alliance” is a kind of trick. The alliance isn’t the “grassroots campaign” it claims to be. Taxpayers cannot vote for its officials or dictate its policies. If taxpayers say austerity has gone too far, the alliance will not listen. It is a private company dedicated to producing a “pro-enterprise country with lower, simpler taxes”, whether taxpayers want them or not.

So far, it looks like a standard front organisation of the type the far left and corporate right have been sending out to greet credulous journalists for decades. Although it keeps its donors secret, the Guardian found that it was tied into the network of thinktanks, foundations and AstroTurf campaigns billionaires in the Koch brothers mould created to turn the west rightwards. Its belief in the stripped-down state won it evangelical approval and $100,000 from the Bahamas-based Templeton Religion Trust, even though the Jesus of the Gospels’ only utterance on fiscal policy was to tell his followers to render their tax returns unto Caesar.

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Theology aside, the underlying philosophy – if that is not too respectful a term – of the TaxPayers’ Alliance and Vote Leave makes little sense. Shahmir Sanni worked for both. Indeed, from Matthew Elliott, chief executive of Vote Leave and a founder of the TaxPayers’ Alliance, down to IT staff, rightist activists bounced between the two.

The culture of this little world was thoughtlessly libertarian, Sanni told me. If you defended the NHS or showed sympathy for those on welfare, you were a “wet”, an insult that performs the same function on the hard right as “centrist” does on the far left. Wets were at best guilty of faulty thinking and rank sentimentality. At worst, they were renegades. The wetness had to be wrung out of them.

True believers had to admire Donald Trump for bashing the hated liberals and believe in Brexit as a matter of course. Political orthodoxy meant that men and women who claimed to have taxpayers’ interest close to their hard hearts never felt they needed to explain what they were doing to taxpayers. Brexit will hammer the tax base. You can take your pick of the forecasts. The UN special rapporteur’s analysis on poverty in the UK said: “Tax revenues will fall significantly. If current policies towards low-income working people and others living in poverty are maintained in the face of these developments, the poor will be substantially less well off.” City sources estimate that the Treasury could lose £10bn a year from the London financial sector alone.

I could take this as a cue to excoriate Jeremy Corbyn and the far left, who spent their lives accusing Labour governments of “betrayal”, yet are ready to back a Brexit that will betray the poorest people and poorest regions in Britain. But frankly, if you haven’t clocked their political bankruptcy yet, you never will.

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As significant are the equally treacherous fiscal conservatives, who rushed to support a shuddering change that will place a greater burden on the taxpayers they claim to support. The conventional liberal-left explanation is that Vote Leave, the TaxPayers’ Alliance, Boris Johnson, Michael Gove and all the other Tory politicians who marched under their banners are operating in the interests of the super-rich, not the 17.4 million people who voted to leave. The financiers behind the investment fund Jacob Rees-Mogg founded can neatly sidestep Brexit by moving assets into the EU; the rest of us will be stuck with stagnation and decline.

But there was never a coherent set of principles behind the Leave campaign, or even a logically thought-through class interest. Instead, there’s a jumble of contradictory imperatives, nurtured in groupthink and sustained by careerism: cut immigration; boost the economy; protect the hardworking taxpayer; threaten the tax base. In what ought to be a notorious moment, Vote Leave refused to define what a vote for Brexit might mean for fear that its own supporters wouldn’t buy it and its flaws would become a target for the Remain campaign.

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In what is certainly its most despicable moment, the TaxPayers’ Alliance fired Sanni after he revealed to the Observer how Vote Leave had circumvented election spending limits. The Electoral Commission has vindicated his stance, but Stephen Parkinson, a Vote Leave director and aide to Theresa May, punished him by revealing that Sanni was gay. (Sanni is from a traditional Muslim family and Parkinson did not care if he destroyed his relationship with his parents.)

The TaxPayers’ Alliance claims to defend the common man and woman from the overbearing state. Yet the clique’s first reaction to a whistleblower was to use the overbearing state to punish the heretic by invading his privacy.

The men who led us into this crisis refused to think through what they were doing. It wasn’t so much that they were never honest with the country about Brexit. It was that they could never be honest with themselves. If they had, Britain’s position might now be less perilous.

• This article was amended on 27 November 2018 to remove a reference to Big Brother Watch.

• Nick Cohen is an Observer columnist