Bets are "pouring in" backing Yvette Cooper to become the next Labour leader putting her joint favourite with Keir Starmer, a bookmaker has said.
And while Ladbrokes has "taken a few small bets" on Jeremy Corbyn being Prime Minister after the 8 June general election a spokeswoman said it was "nothing that has left our trading department quaking in their boots just yet".
Ms Cooper, whose husband Ed Balls has said he will not try to regain the parliamentary seat he lost in 2015, took Theresa May to task at PMQs on Wednesday and claimed voters "cannot believe a word she says".
She said: "The Prime Minister yesterday said she was calling a general election because Parliament was blocking Brexit.
"But three quarters of MPs and two thirds of the Lords voted for Article 50 - so that's not true, is it? A month ago she told her official spokesman to rule out an early general election, and that wasn't true either, was it?
"She wants us to believe she is a woman of her word. Isn't the truth that we cannot believe a single word she says?"
The fiery contribution led Conservative Scottish Secretary David Mundell to shout "Leadership pitch!"
Ladbrokes had Ms Cooper 5/1 as the joint favourite to become the next permanent Labour leader on Thursday.
It came as the betting comparison site Oddschecker showed nearly 42 per cent of punters trying to guess who would occupy 10 Downing Street this summer had put money on Mr Corbyn, compared to just 32 per cent on Theresa May - who is widely thought to be the most likely resident.
Meanwhile Betfair said that on its Exchange site, where people set their own odds and bet against each other, 30 per cet of bets had been on Mr Corbyn and that there was "growing support" for the Islington North MP.
Both Ladbrokes and Betfair declined to draw comparisons with the US presidential election last autumn in which Republican Donald Trump triumphed, because of the short time-scale involved and the predicted result of the UK contest - a crushing Conservative win.
Ms May's party is on on 48 points, compared to Labour's 24, with the Liberal Democrats on 12 and Ukip falling to seven, according to a YouGov/Times survey.
The Ladbrokes spokeswoman said: "In terms of comparisons with the US Election it would be unfair to do that as this is the most lop-sided contest we've seen in decades."
Up to £20 million will be wagered over the coming weeks across the UK, she said.