Conservative leadership hopefuls will find it harder to become Prime Minister after the 1922 Committee changed the rules for the contest.
Candidates now must secure the support of eight MPs in the first round of voting, instead of the two required in 2016.
They then must secure votes from 17 MPs in the first ballot, and at least 33 in the second to remain in the contest.
1922 Committee member Sir Bernard Jenkin said the change will “put a stop” to MPs joining the race to boost their profile.
The 1922 Committee was formed in April 1923, following an initiative by Conservative MPs elected at the 1922 election.
It was hoped the Committee could give a voice to Conservative backbenchers and promote co-operation within the party.
By 1926, all backbench Tory MPs were permitted to become members.
Frontbenchers are now allowed to attend meetings but have no voting rights.
What can they influence?
The committee has little influence over day-to-day policy.
However, it is responsible for organising leadership ballots, including the vote in December 2018 that saw Theresa May survive as leader.
Labour has no such committee that can bring down its leader.
Who are the key players?
The group's 18 members assemble weekly when Parliament is in session.
All six members of the executive committee backed Brexit, and it has long been controlled by the Conservatives’ Eurosceptic wing.
Sir Graham Brady had served as chairman of the 1922 Committee since 2010.
He stepped down as chairman in May for what was widely tipped to be a run for the leadership; however he is yet to launch his candidacy.
Dame Cheryl Gillan is the only female member of the executive committee and is currently acting as its joint chair. The Chesham and Amersham MP was elected to Parliament in 1992, and became one of two vice-chairs in 2015.
Along with Charles Walker she will oversee the leadership vote.
Charles Walker has been vice-chairman of the committee since 2010, and was elevated to joint acting chair last month with the resignation of Sir Graham. The Broxbourne MP has lived with obsessive-compulsive disorder for more than 30 years, and revealed his mental health issues in 2012.
He opened up about some of his daily difficulties, saying: “I have to wash my hands four times. I have to go in and out of a room four times”.
Sir Bernard Jenkin told talkRADIO’s Julia Hartley-Brewer the new leadership rules won’t “make any difference to the outcome”. He is also known as Parliament’s most famous naturist.
Kemi Badenoch is seen as a rising star in the Conservative Party. She apologised in May last year after admitting she hacked into Labour MP Harriet Harman’s website and altered its content. She said: "This was a foolish prank over a decade ago, for which I apologise."
John Lamont is possibly among the fittest of the Committee members, having completed the 2018 London marathon in 3:38:03. He said meeting broadcaster Chris Evans at the start line was a source of “amazing motivation”.
William Wragg was elected to Parliament in 2015 at the age of 27. He had previously worked as a primary school teacher and revealed he was gay on Twitter. He said: "Yes I’m gay. It isn’t everything”.