Former Chancellor Philip Hammond has said he will not stand in the upcoming general election after 22 years in Parliament.
The Conservative MP made the announcement on his Twitter account, sharing a letter to his constituents in Runnymede and Weybridge.
Mr Hammond said in the letter that the decision came with "great sadness" but that the upcoming poll had presented him with an "acute dilemma".
Since he had the Conservative whip withdrawn in September, along with 20 colleagues, he can no longer stand for the party.
However, having been a memeber the party for 45 years, Mr Hammond said: "I remain a Conservative and I cannot, therefore, embark upon a course of action that would represent a direct challenge in a general election to the party I have supported all my adult life."
During his two decades in the House of Commons, Mr Hammond has taken on Cabinet roles including Defence Secretary, Foreign Secretary and most recently Chancellor under Theresa May.
The 63-year-old has been at odds with Boris Johnson's government over Brexit and was ousted from the party voting against the government and backing the Benn Act, aimed at preventing no deal.
Mr Hammond wrote: "The Conservative Party that I have served has always had room for a wide range of opinions an has been tolerant of measured dissent.
"Many parliamentary colleagues have defied the party whip on occasions without any action being taken against them."
He promised to remain an "active member" of the party and make the case for "doing whatever is necessary" to secure a "close future trade and security partnership" with the EU.
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