Conservative MP Andrew Bridgen was arrested today on suspicion of sexual assault and released on bail.
It is understood the 46-year-old MP for North West Leicestershire was arrested in relation to allegations of assaulting a 29-year-old woman in central London in the early hours of this morning.
Mr Bridgen is a married father-of-two, who entered Parliament at last year's General Election, and is regarded as being on the right of the party.
Scotland Yard said in a statement: "A 46-year-old man has been arrested on suspicion of sexual assault against a 29-year-old woman at an address in SW1 in the early hours of this morning.
"He has been bailed to return on a date in mid-July."
Police declined to confirm the identity of the arrested man. A spokesman indicated that the address in SW1 - the London postcode which includes Westminster - was not the Houses of Parliament.
A Conservative spokesman declined to confirm whether the MP involved was a member of the party, saying only: "It is a matter for the police."
Mr Bridgen and wife Jacqueline were married in 2000 and have two sons, Alexander and Benjamin.
After training as an officer in the Royal Marines, he worked for his family's gardening business and set up vegetable firm AB Produce with his brother in 1988.
In the Commons, he is a member of the Regulatory Reform Select Committee.
Since winning the former Labour seat of North West Leicestershire with a majority of 7,511 in the May 2010 election, Mr Bridgen has attracted attention in the Commons as a campaigner against the Alternative Vote in the referendum on electoral reform.
This week he defended Health Secretary Andrew Lansley's plans for radical NHS reform, warning that any watering down of his proposals would amount to "caving in to Stalinist protectionist elements".
Mr Bridgen also spoke out against the use of taxpayers' money to help fund a film starring Meryl Streep as Margaret Thatcher, which is thought likely to be critical of the former prime minister.