Boris Johnson has stripped the Tory party whip from senior MP Tobias Ellwood after he refused to support the Government in the vote of confidence.
It means the long-time critic of the Prime Minister will no longer be able to vote alongside fellow MPs in the Conservative leadership election.
Mr Ellwood is supporting Penny Mordaunt, who is seen as the greatest challenger to Liz Truss, who is being backed by Mr Johnson's allies, to make it into the final two vying for No 10.
The former minister who chairs the Commons Defence Committee argued he was unable to travel back from a meeting with the president of Moldova because of the "unprecedented disruption".
But a Tory source said: "Other Conservative MPs cancelled foreign trips, left poorly relatives and one MP's mother died on the morning of the vote and still attended and voted."
A source on the 1922 Committee of backbench Tories in charge of the leadership election confirmed that those who lose the Tory whip, meaning they are kicked out of the parliamentary party, can no longer vote in the race.
A spokeswoman for the Tory whips' office said: "Tobias Ellwood MP has lost the Conservative Party whip following his failure to vote in support of the Government in the confidence vote last night."
MPs voted 349 to 238, majority 111, to support the motion stating that the Commons has confidence in the Government.
The victory means that Mr Johnson is expected to continue in Downing Street until September, when Tory members chose the winner from the final two selected by Tory MPs.
Mr Ellwood, who was first elected in 2005 as Conservative MP for Bournemouth East, said: "Following my meeting yesterday with the President of Moldova I was unable to secure return travel due to unprecedented disruption both here and in the UK.
"I am very sorry to lose the whip but will now continue my meetings in Ukraine promoting the Prime Minister's efforts here and specifically seeking to secure the re-opening of Odesa port - so vital grain exports can recommence."
Nadine Dorries, the Culture Secretary and ally of Mr Johnson, said suggestions the Prime Minister was trying to remove a vote for Ms Mordaunt by stripping the whip from Mr Ellwood was "wholly untrue".
She responded to such a claim on Twitter, saying: "This is wholly untrue and frankly utterly ridiculous.
"Every single MP of every party is under no illusion regarding the price to be paid in not voting during a Gov confidence motion. It's a very clearly defined and historic red line.
"Tobias could have voted like everyone else."
