Predictions of a Margaret Thatcher-style landslide for the Tories under Boris Johnson has prompted a row among data experts.

The new poll, conducted by ComRes for the Daily Telegraph, said Mr Johnson was the only leadership contender who could offer victory for the Tories in a general election, translating to a majority of 140 seats.

Ahead of Mr Johnson's campaign launch on Wednesday, the survey of some 2,000 voters showed Mr Johnson would boost Tory support from 23 per cent to 37 per cent, putting the party 15 points ahead of Labour.

Analysis by Electoral Calculus, a separate firm, translated this support into a 140-seat majority if Mr Johnson was prime minister - only four less than the party won under Mrs Thatcher in 1983.

Martin Baxter, of Electoral Calculus, told the paper: "With public opinion so divided, a party only needs around 30 per cent support to get a majority at Westminster.

He added: "The poll indicates that Boris Johnson could win back large numbers of voters from the Brexit Party and could win a substantial majority over a divided opposition.

"Other leadership candidates would not have the same effect, although Dominic Raab could keep the Conservatives as the largest party.

However several experts cast doubt on the interpretation of the figures, with one saying it was "bonkers" to project national opinion polls onto constituency results during such political uncertainty.

Philip Cowley, professor of politics of Queen Mary University of London, said voters are "terrible at predicting their own future behaviour at the best of times", let alone during the Brexit chaos.

He added: "Projecting from national opinion polls to constituency results is always tricky.

"When the vote is splitting all over the place as here, it is just bonkers."

Who is standing to be the next prime minister? Show all 3 1 /3 Who is standing to be the next prime minister? Who is standing to be the next prime minister? Boris Johnson - 157 votes Foreign Secretary Boris Johnson arriving in Downing Street, London, for a Cabinet meeting where Theresa May will brief on her plans for Brexit before a major speech aimed at helping to break the deadlock in the negotiations with Brussels. PA Who is standing to be the next prime minister? Michael Gove - 61 votes LONDON, ENGLAND - JUNE 07: Britain's Environment Secretary Michael Gove leaves 10 Downing Street on June 7, 2018 in London, England. Prime Minister Theresa May is holding an emergency Brexit cabinet meeting in an attempt to resolve tensions over the UK's Irish border plan. (Photo by Simon Dawson/Getty Images) Getty Who is standing to be the next prime minister? Jeremy Hunt - 59 votes Health and Social Care Secretary Jeremy Hunt leaving Downing Street, London, after attending a Cabinet meeting. PA

Anthony Wells, director of political research at YouGov, a rival pollster, said hypothetical questions were "pretty dubious" as they seek views conditional on a speculative situation.

“We're asking people to say how they'd vote in an election with leaders they don't know much about, with unknown policies and unknown circumstances," he posted on Twitter.

“They can still sometimes be useful though - you need to understand the actual mechanics of what is going on.

“In this case, it seems to be down to recognition and returning Brexit Party voters.”

Mr Johnson’s prominence compared to lesser known candidates, such as Rory Stewart, may have inflated his score, as some Tory voters said ‘don’t know’ when asked about Mr Stewart, he said.

Mr Wells added: "Brexiteer voters appear to trust Johnson at this point....hence the poll result...but that trust is presumably conditional upon him actually delivering by 31 October.”

Veteran pollster Professor John Curtice said hypothetical polls should be "treated with caution" but said the data was clear that Mr Johnson was coming out on top.

He told The Independent: "It doesn't matter what criteria you use, Boris Johnson wins virtually every single time and in particular he clearly appeals to those who voted for the Brexit Party two weeks ago.

"If you look at the ComRes poll, basically what is going on when people are asked about Boris, the Leave/Brexit vote switches back to the Tories in quite substantial numbers.

"He loses a bit amongst the Remainers but there is a very clear net effect. In this particular poll, nobody else has anything like the same effect."

ComRes chairman Andrew Hawkins said his organisation had never attempted to translate vote share into seats as it was a "perilous activity" but he was confident of its data.

"When it comes to the basic premise that Boris is the most popular candidate, it seems to me that all the underlying data point very clearly in the same direction," he said.

Mr Hawkins added: "We wouldn't as a polling firm, as a policy, criticise other polling companies and I would hope that we would be humble enough to admit if we had got it wrong - but I don't think we have."

ComRes interviewed 2,017 GB adults online between 7th and 9th June 2019. Data were weighted to be demographically representative of all GB adults by age, gender, region and social grade.