Jeremy Corbyn is under pressure to push for a second referendum on Brexit, and even to campaign to remain in the European Union.

Senior voices in Labour are making almost directly-contradicting predictions about what would happen if it adopts a pro-remain stance. Some prophesy electoral oblivion while others say it’s the only way to topple the Conservatives.

So who’s right? Of course, there’s no certainty about any of this — the only poll that really matters is election day itself, whenever that arrives — but let’s take a look at the evidence we do have.

How are the parties doing?

Figures out today from Electoral Calculus predict that as it stands, Labour could expect to lose eight seats in a general election compared to its 2017 total.

It’s touch-and-go who would be the largest party, but both Conservatives and Labour would be “about 70 seats short of a majority”.

That calculation is based on “recent national polls in detail for both European and Westminster elections” and accounts for the fact that some voters defected to “pro- and anti-Brexit parties to make a short-term protest” in the European elections.

It looks pretty grim for both the current government and the official opposition.

Could enticing Lib Dem voters be the answer?

The founder of Electoral Calculus, Martin Baxter, told FactCheck that a 5 per cent swing from Lib Dems to Labour would see Labour gain 47 seats compared to the number it won 2017 election.

In that scenario, Labour would become the largest party in parliament and just 17 seats shy of an overall majority. Jeremy Corbyn would almost certainly be Prime Minister, either with a coalition partner or as head of a minority government.

This begs the question: how could Labour woo the Lib Dems?

Some 22 per cent of Labour voters switched to the Lib Dems in the European elections, according to polling published today by Conservative peer Lord Ashcroft. A further 17 per cent opted for the Greens — another party associated with remain.

As FactCheck reported yesterday, people pick parties for a range of reasons. But it’s hard to escape the fact that the Liberal Democrats are, for the most part, considered a pro-remain outfit. So backing a second referendum and adopting an anti-Brexit stance seems an obvious way for Labour to win over Lib Dems.

Backing Remain is also likely to shore up Labour’s existing base.

FactCheck has seen a report by the Labour-affiliated TSSA union from February 2019 which found that 60 per cent of Labour voters said they’d be more likely to vote Labour if the party was committed to opposing Brexit. Some 28 per cent said it would make no difference, and just 12 per cent said they’d be less likely.

The data is now a few months old, but we note that nearly all of the TSSA predictions on how a pro-Brexit third party might fare were borne out in Thursday’s European elections.

Wouldn’t Labour leavers ditch the party?

The TSSA report, which also used polling by YouGov, offers evidence that Labour Leave voters care less about Brexit than other Leavers.

It found that just 36 per cent of Labour Leave voters list Brexit as one of the top three issues facing themselves and their families (compared to 60 per cent of Conservative Brexiteers).

Only 66 per cent of Labour voters who backed Leave in 2016 say they would do so again in a second referendum, the report finds. Some 16 per cent say they’d now vote Remain, while 13 per cent say they don’t know.

All of this suggests that Labour Leavers are less committed to leaving the EU than Brexiteers in other parties — and therefore less likely to desert Labour if it adopts a pro-Remain stance.

FactCheck verdict

We don’t have a crystal ball, and polls are notoriously difficult to get right. But the evidence available suggests that Labour would benefit from adopting a pro-remain stance at a general election.

The Electoral Calculus site predicts that with just a 5 per cent swing from the Lib Dems, Labour could make a net gain of 47 seats and become the largest party in the Commons — enough to put Jeremy Corbyn in Downing Street.

From what we’ve seen, backing remain is unlikely to drive out significant numbers of Labour leave voters, who tend to put Brexit lower on their list of priorities than pro-Brexit supporters of other parties. Just 12 per cent of those who voted Labour in 2017 say they’d be less likely to do so again if the party backs remain.