Imran Ahmad Khan has said he will resign as MP for Wakefield after he was found guilty of sexually assaulting a 15-year-old boy.
When the guilty verdict was handed down, the 48-year-old was thrown out of the Conservative Party.
A spokesman for the Tories said Ahmad Khan had been expelled “with immediate effect”.
His resignation now triggers a by-election for his former seat of Wakefield in West Yorkshire.
In a statement posted to Twitter, Imran Ahmad Khan said: “While legal proceedings are ongoing, I do not believe that it would ordinarily be appropriate to resign.
“However, owing to long delays in the legal process, my constituents have already been without visible parliamentary representation for a year. Even in the best case scenario, anticipated legal proceedings could last many more months.
“I have therefore regrettably come to the conclusion that it is intolerable for constituents to go years without an MP who can amplify their voices in Parliament.
“Representing them has been the honour of my life, and they deserve better than this.
“Consequently I am resigning as MP for Wakefield and withdrawing from political life.”
Earlier this week, he was found guilty at Southwark Crown Court of sexually assaulting a 15-year-old boy at a house in Staffordshire in 2008.
Mr Khan forced the boy to drink gin at a party 14 years ago before dragging him upstairs, pushing him onto a bed and asking him to watch pornography, a court heard.
Now he has apologised to his family and the community for the “humiliation” but he said he plans to clear his name.
Imran Ahmad Khan added: “I shall shortly write to the Parliamentary authorities to confirm this.
“I am now able to focus entirely on clearing my name. As I intend for this to be my only statement, I would like to apologise to my family and community for the humiliation this has caused them.
“Questions surrounding sexuality in my community are not trivial, and learning from the press about my orientation, drinking, and past behaviour before I became an MP has not been easy.”
His legal team has vowed to appeal against the conviction.