I started my first job at Westminster in 1994, more than half a lifetime ago. Almost all of my career has been spent watching politicians, talking to politicians, writing about politicians. I covered the case for war in Iraq and the war’s dismal descent into failure. I was part of the Telegraph team writing about MPs expenses. I’ve written about more ministerial resignations, scandals, failures of public policy and abdications of leadership than I can remember. None of those failures has ever left me quite as bewildered and despairing as I am today, pondering the latest act in the national farce that is Brexit. Bewildered, despairing and surprisingly angry.

Surprisingly because I don’t often get angry with politicians. One of my many failings as a political writer is a reluctance to condemn. Maybe I’ve been captured after years of proximity and familiarity, but I generally see politicians as just as weak and flawed and human as anyone else – no better than the rest of us, but no worse either. But while we all make mistakes, all sometimes lack a little courage, I find it hard to forgive lying. Especially deliberate, persistent and – most of all – consequential lying. And that is really what the Brexit mess is all about: lying. Pretty much everyone involved in this whole sorry mess is lying about something, and sometimes about more than one thing.

It’s hard to know where to begin with the list of lies and liars, but I suppose my old chum David Cameron is as good a start as any. He lied about Europe and immigration: he knew very well it wasn’t the poison that the liars of Ukip said it was. But instead of challenging the lies, he went along with them, then lied by suggesting he believed Britain’s EU relationship was fundamentally flawed, when in fact he knew it worked fairly well. Then he lied about how much he could achieve by renegotiating that relationship, and lied about how much he’d actually achieved in that renegotiation. Then he fought a referendum offering an end to the EU membership that he’d just (falsely) told the electorate was rubbish.

In the referendum campaign, he faced colleagues and friends who cheerily lied throughout: the “£350m for the NHS” lie was deliberate, intended to put a row about EU contributions in the headlines for days. Lies that Turkey was joining, which implied that migrants from Syria and Iraq would soon have free access to Britain, just gilded the decisive lie about immigration being bad for Britain. Special mention here for Boris Johnson, who lied about actually wanting Britain to leave the EU: he wanted to lose the referendum well enough to become Cameron’s inevitable successor.

Instead, Leave won. After Cameron proved he was lying when he said he wouldn’t quit if he lost, the country ended up with Theresa May. Now, I’ve been relatively kind about May of late, and I stand by that: I think her deal is the least bad option open to Britain, and I think her conduct in the Brexit negotiations since June 2017 has been far more sensible and responsible than that of the various colleagues who have resigned over it or just carped from the sidelines without offering viable alternatives.

But she too lied. As home secretary and then as PM, she bought into and promoted the grand lie about immigration, and based her entire approach to Brexit in 2016 on the premise that European immigration was a scourge on Britain that must be stopped at all costs. That led her to make ending Freedom of Movement the conditio sine qua non of Brexit, and from her decision to insist on leaving the Single Market, another of the major lies of Brexit descends: the lie that leaving could make us better off.

Over the last couple of years, sometimes even sensible people like Philip Hammond have said things like “no one voted to be poorer”. Well actually, yes they did.

Leaving the EU will be bad for the UK economy. It will mean we are poorer than we would otherwise be. That means less money in our pockets, less tax in the Exchequer, less health, wealth and, quite likely, happiness. Why? Because we have chosen to leave a first-class free trade deal with our biggest trading partners in the hope of contracting (at best) second-rate free trade deals with (at best) second-order trading partners.

So if you voted for Brexit, you voted to be poorer. Anyone who says otherwise is lying. They’re either lying unwittingly, because they somehow don’t understand that simple economic truth above, or lying deliberately because they aren’t willing to tell people that truth. May is one of many to fall into that second category; she wouldn’t have become PM otherwise, I suppose.

Perhaps it would have been better to have had a true Brexit believer in No 10, because a Leaver might have been able to be more candid about the realities and compromises of leaving. But then, when you consider the record of prominent Leavers in office, that idea seems optimistic, to say the least:

Consider David Davis in the House of Commons in January 2017:

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“What we have come up with is the idea of a comprehensive free trade agreement and a comprehensive customs agreement that will deliver the exact same benefits as we have, but also enable my right hon. Friend the Secretary of State for International Trade to go and form trade deals with the rest of the world, which is the real upside of leaving the European Union.”

Davis and his fellow Tory unicorn-traders aren’t the only subscribers to such fantastical lies, of course. Jeremy Corbyn’s dishonesty over Brexit takes many forms. He too has suggested it’s possible (and desirable, even) to leave the Single Market while retaining frictionless trade, to stay in the customs union and have a British say on trade policy. He too has blamed imported “cheap labour” for pushing down wages, and inveighed against Freedom of Movement. He’s even talked about the “benefits” of Brexit. But of course, his biggest lie is the one he tells to the supporters who want to stay in the EU, possibly by way of another referendum. Because, of course, he wants Britain to leave.

What about those who don’t want to leave, who want to reverse the referendum result and ensure British membership continues? Aren’t they being honest, at least? If only they were. One of the common lies on the Remain side is that this is all May’s fault, that the PM somehow singlehandedly and secretly led Britain to its current brink. In the age of lies, even events less than two years ago cannot be recalled honestly. So MPs who voted in favour of the most consequential decision of the Brexit process now brazenly complain that May did not take more time and care over her negotiation. I politely suggest that if you’re one of the 498 MPs who voted in February 2017 to authorise May to invoke Article 50 – even though neither she nor the country had settled on clear objectives for our exit – you should now think long and hard before rejecting the deal that she brought back from Brussels after following the process you endorsed. Or at least, be honest enough to say you played a part in setting the conditions for what you now say is a shambolic disappointment.

The biggest lie of the Stop Brexit side is the one about respect. Not about respecting the 2016 referendum result – which is no more sacred than any other vote – but respecting the people who cast the majority of votes in it. They, not the constitutional status of the referendum itself, are the reason Britain has to leave, even though leaving is a bad idea. And – no matter how hard Remainers try to misrepresent marginal shifts in polling data, those voters haven’t changed their minds. Which is hardly surprising, given the lack of honesty some Stop Brexit campaigners show about listening to them and respecting their views.

Me, I agree with Chuka Umunna of the People’s Vote about a second referendum. More precisely, I agree with what he said, honestly and truthfully, in December 2016:

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'I really have no time for calls for a second referendum because I think it comes across as disrespectful to those who voted to leave. Those calls reinforce what I feel is a false stereotype — of a bunch of people in London who think they know best. We are going to leave — it hurts me to say that — but we have got to move forward and work out how to get the best possible deal.'

Which is, at least in terms of the negotiation process since the 2017 general election, what Theresa May has done. Her deal is, more or less, the best possible deal that could have been negotiated within the conditions she and political consensus have imposed: leave the Single Market; end Freedom of Movement; no hard border on the island of Ireland; no customs border in the Irish Sea.

“Best possible deal” doesn’t mean “good deal”, of course. It isn’t a good deal, in the sense of one that delivers significant benefits. But it is better than all the alternatives – or more correctly, less bad than all the other bad alternatives.

Not that May will put it that way. She’d be much more persuasive if she did. But here we come to another dishonesty. Having voted to Remain, May thinks she honours the referendum result and Leave voters by adopting the falsehoods that underpin the Leave cause, especially the notion that Brexit is some sort of opportunity to be seized. Nor has she ever spelled out clearly enough the compromises that those conditions above would necessitate. That contributed to Westminster’s surprise at her perfectly predictable deal, surprise that helped make that deal unsellable.

Though to be fair, May’s lack of candour was a less significant factor in that surprise than simple carelessness: people who sit in Parliament and – especially – who served in her Cabinet before last December really shouldn’t be allowed to get away with claiming they weren’t informed about the implications of May’s approach. There are only two possible explanations for Johnson and Davis suggesting they were surprised by the Chequers deal in the summer: incompetence or dishonesty. Neither quality is a recommendation for the premiership they both still seek.

In short, many of the people who advocate Brexit are lying about the economic harms it will do, while many who advocate no Brexit are lying about the political harms that would do. How many? Enough to leave May’s deal stalled in Parliament, and Britain drifting ever closer to the precipice of a No Deal exit. (I haven’t bothered to even mention the lies of the No Deal crowd: what’s the point?)

And where do all these lies leave us? In today’s mess. The Prime Minister has negotiated the least bad deal possible under the circumstances, but she won’t be honest enough to say it’s a bad deal because delivering Brexit can only mean some sort of bad deal. Nor will enough MPs face up to that difficult fact. Partly that’s because May hasn’t been honest enough about the compromises she’s had to make. Partly it’s because they haven’t paid enough attention to the process to understand that this bad deal was inevitable. But mostly because they don’t have the courage and honesty to say to the electorate that in June 2016, the British people – in a democratic vote, with the facts available to them if they chose to study them – made a decision that leaves the country with the unavoidable task of choosing between bad options.

No one wants to tell the 52 per cent the truth that they voted for bad choices; no one wants to tell the 48 per cent that means we have to pick one of those bad choices. The result is that the least bad option can’t go forward because too many people still believe there’s something better on offer.

And the country, this country that could once claim to set the standard for political stability and solid common sense, is ruddlerless and bereft of leadership. Because so many politicians, the politicians I’ve spent my adult life talking to, writing about and often defending, have failed in their first responsibility: to tell people the truth. And that is where this column ends, because I have no idea of what follows on from that failure.

Perhaps more dishonesty will see us out of this mess. Perhaps the EU will pretend to compromise on the deal, May will pretend she’s won some great victory, and MPs will pretend that their efforts enabled that victory. Perhaps it would be a fitting resolution: if lies got us into this trap, maybe lies can get us out. But sooner or later, lies have consequences.