The huge survey of more than 25,000 people revealed that a majority of voters in all 67 of the most marginal Tory seats now want the public to be given a fresh vote.
It comes as Theresa May’s hopes of securing a withdrawal agreement in November appeared to have faded, with Downing Street warning “significant” issues remained after British officials were locked in talks until 2.45am on Monday morning with their EU counterparts.
During a speech at the Lord Mayor’s Banquet at the Guildhall in London, the prime minister insisted the negotiations were now in the “endgame” but warned Brussels she would not be forced into reaching an agreement at “any cost”.
“We are working extremely hard, through the night, to make progress on the remaining issues in the withdrawal agreement, which are significant,” she said.
On Monday it was reported that Michel Barnier – the EU’s chief Brexit negotiator – told EU foreign ministers that main elements of a withdrawal treaty were ready to be presented by Ms May to Tuesday’s cabinet meeting.
Downing Street reacted with anger at the remarks and the prime minister’s official spokesman said: “I’ve talked about taking things with a pinch of salt before. That applies here. I’d apply a bucket of salt to this one. Negotiations are ongoing.”
The government is facing growing calls to let the public decide the terms of Brexit amid deadlock in cabinet and parliament.
Across all 67 seats, an average of 56 per cent of people want the public to be given a Final Say compared to 44 per cent who do not.
The full study will be presented to MPs by the People’s Vote campaign at a special event hosted by The Independent in parliament on Tuesday.
In a foreword to the study, former YouGov president Peter Kellner said: “Support for a People’s Vote is also high in the 67 most marginal Conservative seats – broadly those where the local MP’s majority is below 5,000. In every seat, supporters of a new public vote outnumber opponents. Overall, the margin is 56 per cent support, 44 per cent oppose.
“If anything, these figures understate the support for a new referendum. They show responses to a general question at a time when nobody knows whether there will be a deal between London and Brussels that wins the support of parliament. Other YouGov research suggests that if there is no such deal, support for a public vote rises.”
Mr Kellner also warned politicians to beware of the “private majority” of voters, who he said comprise almost four in five voters.
People in this group are happy to discuss Brexit in private, he said, but do not tend to do so in public, including with politicians or journalists. Mr Kellner said many “are having second thoughts about the wisdom of leaving the European Union”.
Commenting on the findings, Guto Bebb, Conservative MP for the marginal seat of Aberconwy and a supporter of the People’s Vote campaign, said: “Giving the public the final say on these negotiations is the right thing to do because – whether it’s a no-deal Brexit or the kind of blind Brexit currently being proposed – it will be a miserable result.
“I’m backing the People’s Vote campaign because it’s the right thing to do for our national interest, as well as for businesses and families in Aberconwy. But it’s also really important that Conservatives like me listen to voters rather than just an ideologically motivated rump of my party.”
The survey also found that a majority of voters in the Labour constituencies that voted Leave in 2016 now back a fresh referendum, by an average of 59 per cent in favour compared to 41 per cent against.
And a significant majority of all voters want Britain to continue to be able to trade freely with the EU, even if it means fewer controls on immigration.
62 per cent of people who expressed an opinion said they would rather preserve free trade than cut immigration, compared to 38 per cent who said the opposite.
Among Labour voters the split was 80 per cent to 20 per cent, while frictionless trade was seen as more important than ending free movement even in many Labour seats that voted Leave in 2016.
But Ms May insisted the British people “want us to get on with delivering Brexit”.
In her speech on Monday evening she continued: “The Brexit talks are not about me or my personal fortunes. They are about the national interest – and that means making what I believe to be the right choices, not the easy ones.”
She added: “Overwhelmingly, the British people want us to get on with delivering Brexit, and I am determined to deliver for them.
“I want them to know that I will not compromise on what people voted for in the referendum. This will not be an agreement at any cost.”
Ms May will face further pressure on Tuesday, with Labour seeking to use an arcane parliamentary device known as a “humble address” to force ministers to release any legal advice on the Irish border backstop.
It seeks to force a binding Commons vote by presenting a motion asking the Queen to order ministers to release the documents. The method was used last year to force the publication of Brexit impact assessments.
Sir Keir Starmer, the shadow Brexit secretary, said: “It’s simply untenable for the government to put forward any Brexit deal to parliament without providing the legal advice on what’s been agreed.
“At this critical stage, MPs can’t be kept in the dark nor can we risk parliament being bounced into a decision without having all of the facts available.”
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