Defence Secretary Ben Wallace has announced he will not stand to be the next Tory leader.
Mr Wallace had been tipped to be a front-runner, should he mount a campaign, but he said his focus is on his current role and "keeping this great country safe."
After “careful consideration”, he said, and discussion with colleagues and family, he decided not be join the race to be the next prime minister.
Given Mr Wallace's popularity among Conservative party members, whoever he decides to support in the leadership race would be given a huge boost.
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In a statement on Twitter, he said: “After careful consideration and discussing with colleagues and family, I have taken the decision not to enter the contest for leadership of the Conservative Party.
“I am very grateful to all my parliamentary colleagues and wider members who have pledged support.
“It has not been an easy choice to make, but my focus is on my current job and keeping this great country safe.
“I wish the very best of luck to all candidates and hope we swiftly return to focusing on the issues that we are all elected to address.”
Former chancellor Rishi Sunak, Attorney General Suella Braverman, ex-minister Kemi Badenoch and senior Tory Tom Tugendhat have all launched their bids with further announcements anticipated over the coming days.
Foreign Secretary Liz Truss is widely expected to stand, while other potential front-runners include trade minister Penny Mordaunt, Chancellor Nadhim Zahawi, and former health secretaries Sajid Javid and Jeremy Hunt.
These potential contenders have already received endorsements from Tory ranks, despite not yet launching a bid of their own.
MPs Chloe Smith, Julian Knight and Jackie-Doyle Price have backed Ms Truss, while Tory peer and minister Lord Goldsmith has said Mr Zahawi “stands apart from most rivals.” Gosport MP Dame Caroline Dinenage also declared her support for Ms Mordaunt.
The leadership bids to date have coincided with some controversy over the appointment of new ministers to Boris Johnson’s caretaker Cabinet.
Labour shadow minister Steve Reed lashed out at the Conservative Party after Sarah Dines, who reportedly asked an alleged victim of Chris Pincher if he was gay, was made parliamentary under-secretary of state jointly at the Home Office and the Ministry of Justice.
Meanwhile, Mr Spencer said it was up to Andrea Jenkyns to “justify” her actions after she was caught on camera appearing to make a rude gesture while entering Downing Street.
The Tory MP made the sign with her hand as she walked through the black gates, prior to being named education minister.