Theresa May is facing a showdown when she meets the 1922 Committee later.
But what do we know about the century-old group?
- What is the 1922 Committee?
Also known as "the '22", the committee of all backbench Conservative MPs meets weekly when the House of Commons is sitting.
When the party is in opposition, frontbenchers are allowed to attend, although the leader cannot.
When the party is in government and the leader attends, members are said to bang their desks in approval when the chief arrives.
- Where does the name come from?
The Committee takes its name from a meeting of Conservative MPs on October 19 1922.
The MPs successfully ended the party's coalition with the Liberals, bringing down the government of David Lloyd George. The resulting general election was won by the Tories.
- Who is in charge?
The '22 has an 18-member executive committee with a chairman, usually a senior MP, elected by committee members. The incumbent chairman is Graham Brady, MP for Altrincham and Sale West, who was appointed in May 2010.
- What does it do?
The committee keeps the party informed of the backbenchers' mood and opinion on party business. The chairman has considerable influence within the Parliamentary Conservative Party and oversees the election of a new leader.
A leader who loses the confidence of the '22 is likely to find themselves in a precarious position as Cabinet ministers take the committee's views seriously.
- What has it done?
In October 2003 Iain Duncan Smith was dumped as leader after he lost a confidence vote by 75 votes to 90.