A Tory MP has been arrested after a former parliamentary aide accused him of rape, sexual assault and coercive control, according to reports.
The ex-minister, who has not been named, is alleged to have assaulted a woman and forced her to have sex - and the abuse allegedly took place during a relationship, The Sunday Times and Mail on Sunday reported.
The Metropolitan Police said it received allegations on Friday of sexual offences and assault relating to four separate incidents at addresses in London, including in Westminster, between July last year and January this year.
A spokesman for the Met said: "The Met has launched an investigation into the allegations."
A man was arrested on Saturday on suspicion of rape and was taken into custody at an east London police station, the force added.
He has been released on bail to a date in mid-August.
The papers said the allegations were raised with Tory Chief Whip Mark Spencer, and the complainant also spoke to him - but no action was taken.
A spokesman for Spencer said: "The Chief Whip takes all allegations of harassment and abuse extremely seriously and has strongly encouraged anybody who has approached him to contact the appropriate authorities, including Parliament's Independent Complaints and Grievance Scheme, which can formally carry out independent and confidential investigations."
A Conservative Party spokesman said: "We take all allegations of this nature extremely seriously. As this matter is now in the hands of the police it would be inappropriate to comment further."
The investigation comes days after former Conservative MP Charlie Elphicke was convicted at Southwark Crown Court in a separate case of sexually assaulting two women, one of whom was a parliamentary worker.
Douglas Ross MP, who is standing for the Scottish Conservative leadership, called the allegations against a former Tory minister accused of rape "extremely serious".
Speaking to Times Radio, he said: "These are extremely serious allegations and they have to be investigated thoroughly.
"I did see further comments from the Chief Whip's (Mark Spencer) office that they weren't aware of the magnitude of the allegations.
"I can't explain anything further, I wasn't party to any of these discussions but clearly they must be investigated thoroughly, and that's clearly happening with the Met Police.
"But I only know what I've read in the press this morning."
