Tory leadership candidate Rory Stewart has said he is talking with rival Michael Gove about “combining forces” to block Boris Johnson’s bid for 10 Downing Street.

Mr Stewart’s shock announcement comes just hours before Tory MPs take part in the second round of voting to decide a successor to Theresa May as prime minister.

But it was greeted with a cold shoulder by the Gove camp, who said: “We are in it to win it and we would obviously welcome the support of any candidate that wanted to drop out and support us.”

The international development secretary has surprised Westminster by shooting from rank outsider to fourth place in the contest, taking 37 votes on Tuesday to Mr Gove’s 41, with Jeremy Hunt in second place on 46.

But all the contenders lag well behind former foreign secretary Mr Johnson on 126, with the Brexit figurehead apparently assured of a place on the final shortlist of two from which Conservative members will choose a new leader in a postal ballot next month.

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Asked about his talks with environment secretary Mr Gove, Mr Stewart told the BBC’s Victoria Derbyshire Show: “We are talking about combining forces because it is clear that Boris is going into the last round and the question is who is best placed to sit on a stage with Boris Johnson and who is best placed to ask the testing questions he needs to be asked?”

Mr Stewart said he had been up until 3.15am following the BBC TV debate texting fellow MPs to ask for their support in the third MPs’ vote, which takes place today. He said he had picked up two new supporters, though he acknowledged it would be difficult to win over supporters of hardline Brexiteer Dominic Raab, who was eliminated on Tuesday.

Mr Stewart was asked how he could reconcile his outright refusal to contemplate a no-deal Brexit with Mr Gove’s insistence that it is preferable to failing to leave the EU at all.

He replied: “By sitting down and thrashing through that very issue. We would have to sit down and come to a common position on that and I would have to say to him ‘How is it you think you will get a different deal with Brussels and how would you get a no-deal through parliament?’ And we would have to compromise.

“If neither of us were prepared to budge on our analysis, of course we couldn’t combine.”

Other PM candidates 'offering promises they can't deliver' argues Rory Stewart

A member of the Stewart camp said that the international development secretary speaks with other candidates “all the time” and accepts that at some point people will need to combine teams.

“But any team that combines, Rory wants to lead it,” said the campaign source. “He is the only one with a chance to beat Boris in the final two and to provide the clearest choice. He’s the one outpolling in the areas we need to win.

“Rory’s in this to win, whether on his own or with other people coming behind him, and go all the way to the final two and Number 10.”

Mr Stewart issued a list of 10 questions for all candidates to answer on their Brexit policies, including whether they are ready to suspend parliament to force a no-deal Brexit through, what tariffs they expected UK farmers and manufacturers to pay under a no-deal scenario and whether they could rule out a general election this year.