NO SOONER has he clinched Labour’s candidacy for the 2020 London mayoral election than Sadiq Khan has broken ranks with the party leadership to call for another referendum on EU membership.

His intervention comes as we learn that over half the motions submitted to Labour conference concern Brexit, with the bulk of these calling for a second vote.

Khan goes further than the position agreed at last week’s Trades Union Congress. The London Mayor is calling explicitly for any vote to include the option of staying in the EU.

While the majority of unions at the TUC backed a statement which included the option of another referendum, most speakers in the debate — including the TUC general council’s spokesman, Unite’s Steve Turner — emphasised that the priority was a general election to get a Jeremy Corbyn-led government into power, with a so-called “people’s vote” a last resort.

Several stressed the fact that a rerun of 2016’s vote would be deeply divisive. Unite leader Len McCluskey and GMB leader Tim Roache have stated that any second vote must accept the fact that Britain is leaving the EU, confining itself to the terms of departure.

McCluskey remarked that another vote on EU membership itself would be reminiscent of Bertholt Brecht’s famous jibe about government dissolving the people and electing another. The CWU’s Dave Ward was even more emphatic that the time was not right for a second vote when the priority was to unite Remain and Leave voters behind a Labour Party that envisions radical change.

Unfortunately, these subtleties are likely to be ignored as pressure groups calling on the Labour leadership to U-turn on its pledge to respect the 2016 result present a second referendum as the option “backed by the unions.” This is one reason the Morning Star preferred the RMT union’s clear-cut rejection of a second vote, which could not be spun to suit the purposes of Corbyn’s enemies in the Labour Party.

One might well count Khan among these, though he has been less intransigent and less offensive than the likes of Chuka Umunna or Margaret Hodge. Khan joined the calls for the Labour leader to step down in 2016, claiming the party could not win under Corbyn’s leadership, and he piled in with the barrage of accusations that the leadership had an anti-semitism problem as well.

There are further reasons the Labour leadership should be wary of Khan’s advice. A majority of London voters backed Remain in 2016, and the capital city is Khan’s immediate constituency. But a majority of Britain’s voters backed Leave, including in two-thirds of Labour constituencies.

Millions of voters are sure to conclude that no rerun would have been offered had the Establishment recommendation of a Remain vote passed, and will lose faith in a system that keeps them voting till they get the “right” answer — as the EU has done before, in Ireland, the Netherlands and France.

Others argue that people did not vote for the deal being stitched up by Theresa May with Brussels. But the options in 2016 were simple: Remain or Leave. To say that people did not vote for this or that leaving arrangement is as irrelevant as saying after a Remain vote that people had not voted to remain on particular terms (one weakness of the Remain and Reform position, since having remained there would be no mechanism to enforce reform). It will be for a Labour government to strike a deal that represents working people’s interests.

Labour’s seismic advance in 2017 was down to it changing the terms of debate. It accepted the referendum result and fought for a government committed to a radical shift of power and wealth to working people, and it enthused millions.

That achievement could be thrown away if the party becomes a mouthpiece for those who want a return to the past.

Staying in the EU would cause problems for a Corbyn government because of the restrictions it would impose on aspects of the Labour programme, but pledging a second referendum could put the election of such a government at risk in the first place as working-class people who have been told for decades their views don’t matter find that explicitly confirmed. The rapid rise of the far right across Europe shows exactly where that could lead.