Deputy House of Commons Speaker Nigel Evans has been released on bail after being arrested on suspicion of rape and sexual assault.
The Conservative MP, 55, was questioned about alleged attacks on two men in their 20s, the Press understands.
Police said a 55-year-old man was arrested on Saturday morning and was interviewed by officers all day.
The alleged offences took place between July 2009 and March 2013 in Pendleton, Lancashire, police added.
Mr Evans has been bailed until 19 June.
Prime Minister David Cameron has been made aware of the arrest, it is understood.
In a statement, Lancashire Police, who have not named the man, said: "A 55-year-old man from Pendleton in Lancashire has today, Saturday, 4th May 2013, been arrested by Lancashire Constabulary on suspicion of rape and sexual assault.
"The offences are alleged to have been committed in Pendleton between July 2009 and March 2013.
"We take all allegations of a sexual nature extremely seriously and understand how difficult it can be for victims to have the confidence to come forward.
"As a constabulary, we are committed to investigating sexual offences sensitively but robustly recognising the impact that these types of crimes have on victims.
"We would encourage anyone who has experienced sexual abuse, or who has information about it, to have the confidence to report it to us knowing that we will take it seriously, deal with it sensitively and investigate it thoroughly."
Mr Evans, MP for Ribble Valley since 1992, was elected one of three Commons deputy speakers three years ago.