Pressure is mounting on the Conservatives to remove the whip from an MP accused of rape.
The unnamed parliamentarian has been asked to stay away from Westminster by the party after he was arrested on suspicion of rape and sexual assault on Tuesday evening.
The MP, who is in his 50s, has been released on bail pending further inquiries.
The Conservatives’ decision not to remove the party whip at this stage means he can still sit as a Tory MP.
But a spokesman for Labour leader Keir Starmer said: “Given the nature of the allegations that there are, it doesn’t seem to be sustainable to argue that he shouldn’t be suspended from the whip.”
He added: “It’s a matter for the Conservative Party what they do, but our view is that given the nature of the allegations then the whip should be suspended and obviously at that point [his name] would become public.”
Asked whether Starmer would suspend the whip if it was a Labour MP, the spokesman replied: “Yes.”
Scotland Yard said the man was detained on suspicion of rape and sexual assault offences spanning seven years. He has also been accused of indecent assault, abuse of a position of trust and misconduct in a public office.
The Metropolitan Police said officers initially received a complaint about the MP in January 2020.
A spokeswoman for the prime minister said he was “shocked” to learn of the investigation when he was told about it yesterday.
News of the arrest came just weeks after Neil Parish resigned as a Tory MP for watching porn in the Commons.
Imrad Ahmad Khan also quit as the Conservative MP for Wakefield after being convicted of sexually assaulting a teenage boy.
David Warburton, the MP for Somerton and Frome, was suspended over allegations of sexual harassment and drug use.
And Rob Roberts, the MP for Delyn in North Wales, was also suspended by the Conservatives for sexually harassing a member of his staff.
Johnson’s spokeswoman said it was unacceptable that a “small minority” of MPs’ behaviour had fallen below what was expected.
“The vast majority of MPs behave with the respect and decency you would expect,” she said.
“Clearly, there have been a small minority who have not lived up to those expectations and that is not acceptable.”
Asked why the whip had not yet been withdrawn from the accused MP, the spokeswoman said: “While there is an ongoing investigation I hope you will understand that it wouldn’t be appropriate for me to comment on that specific question.
“It’s a matter for the whips.”
It is understood the Conservatives will not make a decision on whether to suspend the whip until after the police investigation is concluded.