THE Scots-born cabinet minister Stephen Crabb is the first to throw his hat in the ring to succeed David Cameron as Conservative leader and prime minister.

The 43-year-old Work and Pensions Secretary will join Sajid Javid, the Business Secretary, on a joint “blue collar” ticket to take on the favourites former London mayor Boris Johnson and home secretary Theresa May.

They have recruited Jeremy Wright, the Attorney General, as campaign manager and will formally announce their bid tomorrow morning ahead of nominations opening; they close midday on Thursday.

Mr Crabb, hugely popular among colleagues, comes from the sort of ordinary background - single mother, council estate, state-educated - that chimes with many voters; indeed, Mr Javid is the son of a Pakistani bus driver, who became a highly successful investment banker.

Both men backed the Remain side though Mr Javid faced claims he was privately in favour of leaving the EU.

Jeremy Hunt, the health secretary, has said he is "seriously considering" a bid as has Scot Liam Fox, the former defence secretary.

However, George Osborne made clear that, because he had been a “full-throttled” Remainer, he would be seen as too divisive so would not be entering the contest, saying that, “at the moment”, he would not be saying who he is backing.

The chancellor’s endorsement could prove crucial. Given that the Prime Minister will not reveal who he is supporting, it could be up to Mr Osborne to give a lead to the Cameronites, many of whom feel embittered about how Mr Johnson triggered the political demise of his one-time friend.

Asked if someone from the pro-EU side could win, the chancellor replied: “Absolutely. I am not backing any candidate at the moment but, of course, I was full-throttled in arguing for remaining in the EU and because half my party wanted to leave the EU I don't think I can be the person who can bring the party together."

This, for some, seemed to point to how he might be prepared to support Mrs May, who conspicuously stood back from the campaign frontline. Initially thought to be a Brexiter, she eventually declared herself for Remain. Some Westminster-watchers have suggested that the Secretary of State might have cut a pre-poll deal with the PM and chancellor to remain in the shadows just in case the Leave side won, so she could then put herself forward as the unity candidate in any subsequent contest.

Others who are also said to be considering throwing their hats in the ring include Education Secretary Nicky Morgan and Brexit campaigners Andrea Leadsom, the energy minister, and fellow Outer Priti Patel, the business minister.

Meantime, sources close to Mr Johnson suggested he would not hold a snap general election if he won the leadership contest.

Senior Tory Sir Nicholas Soames said he was backing the Uxbridge MP to take the top job with Michael Gove, the Justice Secretary, expected to be supporting his bid for the leadership.

The former defence minister tweeted: "Gave @BorisJohnson proper stick during campaign but only one way ahead now. Boris will be great PM. The Gover makes it a top team #GoBozza."

Elsewhere, the timetable for the contest has been extended by a week with Mr Cameron's successor now due to be unveiled on September 9, a month before the Tory Party’s annual conference.

The executive of the party's 1922 backbench committee had recommended that it be concluded by September 2 "at the latest" but the Party Board argued more time was required.

"The Board and the 1922 Committee both agree that the leadership election should take place as speedily as practical considerations allow," a party spokeswoman said.

She added: "In order to ensure there is full participation by the membership, the Party Board recommends that the date of the declaration of the leader is September 9."

Conservative MPs are expected to endorse the schedule later today.