Former Chancellor Philip Hammond has announced he is standing down at the general election, less than four months after he left government.
Mr Hammond tweeted: "It is with great sadness that I am today announcing my decision to stand down as Member of Parliament for Runnymede & Weybridge at the forthcoming General Election."
In a letter to his constituents, Mr Hammond said that having represented them for 22 years it is "not a decision I have taken lightly".
He said the withdrawal of the whip from him and 20 other colleagues in response to their support for the Benn Act means that he is unable to stand as a Tory candidate in the election.
"If I fight the General Election as an Independent conservative candidate against an official Conservative Party candidate, I would cease to be a member of the party.
"I am saddened to find myself in this position after 45 years of Conservative Party membership, 22 years' service as a Conservative MP, 12 years as an opposition front-bench spokesman and over 9 years as a Cabinet minister, including service as Defence Secretary, Foreign Secretary and Chancellor of the Exchequer," he wrote.
Another Tory MP who lost the whip, Anne Milton, has announced she will stand as an independent in her Guildford constituency.