Labour’s Shadow Transport Secretary Louise Haigh said: “A new session of Parliament has started, the Conservatives must allow the people of Wakefield to be represented in it.
“The city has been without an MP for a year while Imran Ahmad Khan was on trial for sexually assaulting a teenage boy. Through the cost of living crisis and the last year of the pandemic local people have been without anyone in their corner.
“Even after being found guilty, the Conservatives allowed their disgraced MP to post-date his resignation causing even more delay.
“The by-election must be called immediately so the people of Wakefield can get back their voice in the House of Commons.”
The Labour Party had held the seat for 89 years, until Khan claimed a shock victory at the 2019 General Election victory. He beat Labour former frontbencher Mary Creagh by 3,358 votes.
Labour has drawn up a longlist of potential candidates, which includes Kate Dearden, Sam Howart, Simon Lightwood and Rachael Kenningham, and on Sunday one will be chosen to represent the party in the by-election.
Reports had suggested Ms Creagh and former Chancellor Ed Balls were interested in running, but they have both ruled themselves out.
Khan, 48, was found guilty of committing sexual assault in 2008, during a trial at Southwark Crown Court last month.
During the trial, jurors heard he forced the teenager to drink gin and tonic before dragging him upstairs and carrying out the attack at a house in Staffordshire.
He has appealed against the conviction, but is still due to be sentenced on May 23.
In his resignation letter, Khan said he intended to appeal against the conviction but “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,” he said.
“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.”
He added: “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.”