Tom Watson knows Boris Johnson might be forced to call a referendum – Labour’s Brexit fudge can’t last

Tom Watson, the Labour deputy leader, has finally come out and said he no longer respects the result of the 2016 referendum. “There eventually comes a point,” he said in his speech today, “when circumstances are so changed … you have to say, actually, no, that years-old plebiscite is no longer a valid basis on which to take such a momentous decision.”

Full marks for intellectual clarity.

Everyone who complains about Jeremy Corbyn sitting on the Brexit fence has to recognise that there are only two coherent positions. Either Labour wants to leave the EU, or it wants to stay. And if the party wants to stay, it has to argue for a new referendum as the only credible way to reverse the original mandate.

For a year now, Labour has argued for part of this case – a referendum – but has refused to say what it wants it for. Yesterday, Corbyn repeated to the TUC the same formula: that a Labour government would put “Remain” versus “a credible Leave option” to the people in a referendum. But he refused to say, either in his speech, or when confronted by Cathy Newman of Channel 4 News on the back stairs afterwards, which side he would back.

We know what he is doing. He is trying to hold together two Labour coalitions. There is the leadership coalition, in which some trade union leaders led by Len McCluskey of Unite, and a minority in the shadow cabinet led by Ian Lavery, the party chair, want to leave the EU. And there is the coalition of the electorate, in which a minority of Labour voters want to leave.

Those coalitions would be hard to sustain in an election. Corbyn couldn’t dodge the question for the whole campaign. He would have to say that he, as a Labour prime minister, would argue for his Brexit deal, or against it, or that he would be neutral. This last option cannot be done in practice: Harold Wilson tried to stay above the fray in the 1975 referendum campaign, but everyone knew which side he was on. Hence Watson’s clarity: a referendum ought to be held before an election. He also echoed Tony Blair’s argument from yesterday – further cementing the Blairite-Brownite rapprochement – that a Brexit decision should be made on its own, uncluttered by the NHS and (as neither of them said out loud) Corbyn’s personal unpopularity.

As Blair put it, Boris Johnson “wants an election because he thinks he can mix up the Brexit question with other issues to his advantage”.

However, there is one big problem with a new referendum: parliament won’t legislate for it. When the indicative votes were held in April, only 280 MPs voted for a “confirmatory public vote” – 40 short of a majority.

Yet there is now a problem with an election too. Labour MPs voted against an election “on Johnson’s terms” (that is, as soon as possible) but really because they fear he would win it. While Johnson is still popular and the Conservatives have a seven-point average poll lead, they will continue to vote against it. But then, if Johnson looks as if he will lose an election, he is unlikely to propose one again, and even if he did his MPs would be unlikely to vote for it.

There is a possible scenario in which an unpopular Johnson, forced to postpone Brexit and unable to fight an election, eventually proposes a referendum as his way out of the box.

Corbyn, I think, would have to campaign for Remain in such a contest. Watson has already put his marker down. In two weeks’ time, Labour’s conference is likely to adjust the party’s Brexit policy in his direction. After that, he may be vindicated and get a referendum before an election after all.