The Metropolitan Police confirmed a man was in custody over allegations dating back to between 2002 and 2009.
The Conservative Party said he had been asked by the chief whip “not to attend the parliamentary estate while an investigation is ongoing”.
The man also faces allegations of an abuse of position of trust and misconduct in a public office.
A Met Police spokesman would not confirm the identity of the man, but published a statement, saying: "In January 2020, the Met received a report relating to alleged sexual offences having been committed between 2002 and 2009.
“The offences are alleged to have occurred in London.”
He added: “A man… was arrested on suspicion of indecent assault, sexual assault, rape, abuse of position of trust and misconduct in public office.”
The force said the investigation was ongoing and being led by officers from the Central Specialist Crime unit.
The latest arrest also follows a Conservative MP being arrested on suspicion of rape in 2020. He was never identified and police took no further action after an investigation.
Making a statement in the Commons, Sir Lindsay Hoyle, the Speaker, said he took “the safety of our staff and parliamentary community as a whole very seriously”.
Sir Lindsay also warned MPs against naming the individual, saying he believed it would be “wholly inappropriate for any further reference to be made to this matter in the House”.
The Metropolitan police have not named him because, in line with College of Policing guidance, they do not usually identify people who have been arrested before they are charged.
The reason why newspapers are also not naming him is more complex and is connected to a mixture of convention and legal precedent going back to the 2012 Leveson report on media standards, which recommended suspects remain anonymous pre-charge.
While many newspapers disagreed with this as a policy, a complication came with the legal case the singer Cliff Richard won against the BBC after the corporation reported he was being investigated over allegations of historical child sexual assault, for which he was never arrested or charged.
These allegations of rape from so long ago sometimes makes me wonder if there isn’t a little bit of “beware the woman scorned” in there somewhere. What might have been a very happy relationship suddenly went pear-shaped for whatever reason and the “harmed party” has only just now decided that none of it was consensual.
That is not for a Forum to decide, it is for a Jury to decide on the evidence available.
Being raped is so humiliating to the victim that it can legitimately take years to be able to report it.
I do not know any of the circumstances of this case, the decision is for a Jury to decide.
I can understand why some would choose not to report it straight away, simply because they want to protect the male members of the family who would kick off.
