Pledging to give the British people a final say on Brexit would see a surge in Labour support that would carry it to the brink of government, according to two separate new polls.
A second unconnected study by ICM of specific constituencies indicated such a pledge would see Labour win enough votes to hold and make gains in marginal constituencies – even in those that backed leaving the EU.
It comes as Theresa May’s push to win support for her Chequers Brexit deal in Europe was thrown into turmoil after all 27 EU member state leaders dashed her hopes of progress and agreed it “will not work”.
Earlier in the day as the prime minister attempted to persuade them of its merits, some called for the British public to be given a fresh vote on Brexit as the options become clear.
The Independent has launched its own campaign for a Final Say referendum on the final Brexit deal, with more than 800,000 having signed the petition so far.
But the new data from two major pollsters sheds light specifically on the impact that backing a new referendum would have on Mr Corbyn’s electoral prospects, with the issue set to dominate Labour’s annual conference starting this weekend.
Ex-president of YouGov Peter Kellner said his former organisation’s poll, commissioned by the People’s Vote campaign, “leaves no doubt that by backing a popular vote on Brexit, the party would end up making significant gains in votes and seats”.
It surveyed a weighted sample of the population numbering more than 10,000 people between 28 August and 4 September, with half saying the EU is the single biggest issue facing Parliament.
[This] leaves no doubt that by backing a popular vote on Brexit, the party would end up making significant gains in votes and seats
Peter Kellner, ex-president of YouGov
Of this group some 37 per cent – equivalent to 7.4 million voters – said they would “definitely” vote Labour or be “more likely” to if the party backs a new vote.
Once those who were already Mr Corbyn’s backers are excluded, along with those who said that despite being more attracted to Labour they would still vote for another party, the proportion left represented 1.75 million non-Labour voters who said they would swing to the party if it backed a new referendum.
Mr Kellner went on: “What about voters who might desert Labour? A substantial minority of Labour supporters voted Leave in 2016. Many Labour MPs fear that support for a referendum could cost them votes at the next election.
“YouGov’s figures do not bear this out. Of the YouGov respondents who currently support Labour and voted Leave in the Brexit referendum, only 6 per cent put Brexit at the top of their concerns and say they would not, or be less likely to, vote Labour if the party backed a popular vote.
“This is just two per cent of all Labour supporters, or just over 200,000 voters in all.”
He explained that once these voters were subtracted from those gained by a pledge to back a new referendum, the net increase is some 1.5 million votes.
Mr Kellner added: “Like all such hypothetical exercises, different ways of asking the questions and doing the sums will yield different results.
“But the nine-to-one gulf between the non-Labour target voters and the at-risk Labour supporters leaves no doubt that by backing a popular vote on Brexit, the party would end up making significant gains in votes and seats. In a tight general election, it could make the difference between returning to government and remaining in opposition.”
With those figures layered on the whole country, Labour would stand to gain around 60 seats across the UK.
The ICM poll, separately commissioned by the group Represent Us, drilled down into specific constituencies by polling in 107 marginal seats across the UK with a majority of less than 3,500.
Across the 82 seats in England and Wales it found Labour would leapfrog the Tories in vote share with a pledge to back the new vote, going from a point behind in 2017 to a point in front, down in large part to stealing support from the Liberal Democrats.
That would indicate Labour holding its 35 most marginal seats in England and Wales and winning a further 16 from the Conservatives – despite at least 38 of these having backed Leave in 2016.
Backing a new referendum would also allow Labour to minimise potential losses against a dominant SNP in Scotland, according to the ICM data.
Dozens of motions have been tabled ahead of Labour’s conference in Liverpool in a bid to get the party to vote on backing a new referendum on Brexit, with several unions having already thrown their weight behind the idea in the run up.
There is also set to be a rally for a People’s Vote on Sunday in Liverpool right outside the party’s main conference event.
The Independent understands that the leadership will likely stick to its commitment to keep the option of a vote on the table, without giving explicit support to one.
Labour MP for Tottenham David Lammy urged his party to back a new referendum, saying: “What these figures show is that supporting a People’s Vote is also the right thing for the party to do if we want to win a general election.
“This should concentrate some minds at our conference in Liverpool next week.”