Old BBC cameramen tell a story about former economics editor Peter Jay. Asked why he had delivered a piece to camera incomprehensible to everyone else, he is said to have replied: “it was intended to be understood by only two people, one of them being the Chancellor”.

This column is intended for a wider audience, but only slightly: it is an open letter to the ten Labour MPs who are reported to be thinking of backing Theresa May’s Brexit deal, either on the grounds of anti-European principle, avoiding chaos, or their critique of the EU as a neoliberal institution. I hope the first sentence does not put them off:

You are in danger of betraying not just the working class and the Labour Party but the national interest of this country. Whatever principles you might be following - and I know a few of you are driven by principle - the obvious practical effect of backing May, when her own rebels are determined to scupper the deal, will be to keep her in power.

If Labour and the other opposition parties can defeat May in the Commons, we stand a chance of triggering a general election, in which Labour wins and Corbyn becomes prime minister. The minimum upside of this is the end of ten years of austerity; an end to the Gestapo treatment of your constituents by the DWP; an end to reliance on food banks; an end to poverty wages, healthcare rationing and zero-hours contracts. To exchange that possibility for something else, you would have to believe that something was better than a Labour government. What is it?

Okay, defeating the deal might not trigger a general election. But it will trigger a change of Tory leadership, a reopening of the terms of Brexit – and a level of constitutional chaos that your constituents, when some of them backed Leave, did not expect. But there is no Wetherspoons, no transport café, no school gate in Britain in which this could be blamed on Labour. It is May, who delayed serious negotiations about a deal in order to compress the timescale for ratification, who will and should be blamed for the chaos.

There are three reasons why a Labour MP might prop the Conservative government up: first, because you desire Brexit at all costs; second, because you fear a right-wing backlash among constituents who might vote Labour, who may feel their democratic choice has been stolen from them; third, that you want to “get on with” bread and butter politics as normal, as do many of your constituents. Let’s take these in order.

The right-wing Brexiteers among the PLP – Frank Field, Graham Stringer and Kate Hoey, who revolted over the customs union amendment in August – are driven by opposition to free movement, and the desire for democratic sovereignty free of Brussels interference. They seem oblivious – and insouciant – about the levels of xenophobia and racism the Brexit vote unleashed, and happy in one case to sit in the lap of Nigel Farage.

But May’s deal in no way expands the UK’s sovereignty. It diminishes it. On this the European Research Group and the Tory Remainers are correct: Britain had greater decision-making power inside the EU compared to leaving on the terms May has agreed with Brussels.

As to a long-term replacement for free movement, the Labour frontbench has committed to this as part of its own vision for Britain after Brexit. So “respecting the wishes of the electorate” on migration is not an argument for keeping May in power.

There are also left-wing Labour MPs who have a record of opposing on principle a form of Brexit which involves a customs union: Laura Smith in Nantwich (majority 48) and Dennis Skinner spring to mind. In their view, the EU is an irreformable neoliberal construct best left to collapse at a distance.

Neoliberal it certainly is, but even if it collapses, May’s deal will ensure the UK is not at any great distance. Indeed, as the European Commission imposes new restrictions on what city governments can do against privatisation and outsourcing, May’s promise of “close regulatory alignment” ensures the UK will be handcuffed to the neoliberal Commission for the foreseeable future. The best way of stopping this, and negotiating a better deal, is to trigger an election, not to keep May in power.

Next come the “terrified of Tommy Robinson” brigade. With Ukip set to admit Stephen Yaxley-Lennon, thus transforming itself into a quasi-fascist entity, Labour activists in Leave-voting areas are right to be concerned about the far-right threat. I’ve reported here and elsewhere how strong grassroots support for hard Brexit remains in many Labour target seats and heartlands. That may be an argument for refusing to support a second referendum, but it is not an argument for keeping May’s zombie government thrashing around in power.

I’ve heard it argued that “May will call an election and make it about the deal, yes or no.” But she can’t. The deal is not supported by her party and would not make it into a Conservative manifesto. There is a chance that she would then abandon the Chequers project completely, switching to a Canada-style trade deal, and losing 10 to 15 Remainers in the process. But that is not the deal she did with Brussels.

So there is no principled reason to keep May in power. Those arguing “we’ve got to put country before party” are forgetting the damage May’s deal will do to the UK’s national interest: economically, geopolitically and in terms of democratic process.

For those who fret about the breakup of Britain - I don’t - there is the added certainty that a deal like this will propel Scotland towards independence within a decade and create the possibility of a united Ireland within two. Indeed, arguing that you have to assuage the prejudices of English nationalist voters “in the national interest” while shafting the majority of Scottish voters is a sure fire way for a Labour MPs to undermine the party’s standing in Scotland.

There is one rational reason for keeping May in power – and that is the one that the hard Brexiteers oddly share with their opposite numbers on the Chuka Umunna wing of Labour: to prevent a government led by Jeremy Corbyn.

As the Italian Marxist Antonio Gramsci once said, the state does not consist of simply the police force and secret service: the elite possess line after line of defences against a government that could represent the interests of working people. One of them is the kind of MP who will walk through the lobby with May simply to keep Corbyn out of office.

As for “let’s get on with normal politics and put Brexit behind us” – forget it. A Brexit deal enacted on May’s terms will leave us with years more negotiations, years more angst as the job losses and disinvestment mount - and years more opportunities for the American far-right to pour money into Ukip and “harder Brexit” campaigns.

Hard Brexit has, in truth, already failed. It cannot happen because there is not enough political support for it even in the Tory party. May’s “cakeism” has run out of cake. All forms of Tory Brexit are destined to fail on their own terms.

So it’s time for a different political leadership in this country. The only way to unite people and move on is a realistic, honest and democratically assessed deal that is then put to a second referendum. The only way to get to that point is through a Labour government. That means defeating May in the Commons in a meaningful Brexit vote.