Nadine Dorries has announced she is standing down as a Conservative MP “with immediate effect”.
In a tweet, the former cabinet minister said: “I have today informed the chief whip that I am standing down as the MP for Mid Bedfordshire, with immediate effect.
“It has been an honour to serve as the MP for such a wonderful constituency but it is now time for someone younger to take the reins.”
Ms Dorries had previously said she won’t be contesting her seat at the next election.
The early resignation means there will a by-election in her constituency and follows reports she has been dropped from Boris Johnson’s honours list.
Ms Dorries, a close ally of the former prime minister, has served as MP for Mid Bedfordshire since 2005 and is also a best-selling novelist.
Her promotion to culture secretary under Mr Johnson’s premiership saw her lead the now-ditched plan to privatise Channel 4.