Lord Mandelson has been released on bail, the Metropolitan Police says, hours after his arrest on Monday on suspicion of misconduct in public office.
The force said a 72-year-old-man was released pending further investigation. The BBC saw Lord Mandelson returning to his London home at 02:00 GMT.
Lord Mandelson was arrested at an address in Camden, north London, on Monday and taken to Wandsworth police station for interview.
The force launched an investigation earlier this month over allegations that, while he was serving as a government minister, Lord Mandelson had passed on market-sensitive government information to the late convicted paedophile Jeffrey Epstein.
