Rebekah Brooks has been arrested by police investigating allegations of phone hacking by the News of the World and allegations that police officers were bribed to leak sensitive information.
The Metropolitan police said a 43-year-old woman was arrested at noon on Sunday, by appointment at a London police station.
Brooks, 43, resigned on Friday as News International's chief executive. She is a former News of the World editor and was close to Rupert Murdoch and the prime minister, David Cameron.
A spokesman for Brooks said she did not know she was going to be arrested when she handed in her resignation.
Brooks was taken into custody at midday on Sunday, after agreeing to attend a London police station for questioning. Her spokesman, Bell Pottinger chairman David Wilson, said she did not know she was to meet with police until late on Friday, and that she did not know the appointment would result in her arrest.
The News International chief executive announced her immediate departure from the company on Friday morning. She had agreed to give evidence this coming Tuesday to the culture select committee's inquiry into allegations of phone-hacking at the News of the World.
Her lawyers are currently in discussion with the committee about whether she should attend. Wilson said: "It's left Rebekah in a very difficult position and has left the committee in a very difficult position".
An arrest by appointment on a Sunday by police is unusual.
In a statement the Met said: "The MPS [Metropolitan police service] has this afternoon, Sunday 17 July, arrested a female in connection with allegations of corruption and phone hacking.
"At approximately 12.00 a 43-year-old woman was arrested by appointment at a London police station by officers from Operation Weeting [phone hacking investigation] together with officers from Operation Elveden [bribing of police officers investigation]. She is currently in custody.
"She was arrested on suspicion of conspiring to intercept communications, contrary to Section1(1) Criminal Law Act 1977 and on suspicion of corruption allegations contrary to Section 1 of the Prevention of Corruption Act 1906.
"The Operation Weeting team is conducting the new investigation into phone hacking.
"Operation Elveden is the investigation into allegations of inappropriate payments to police. This investigation is being supervised by the Independent Police Complaints Commission.
"It would be inappropriate to discuss any further details regarding these cases at this time."