A 23-year-old man has been arrested in connection with the Andrew Mitchell "plebgate" investigation, Scotland Yard said.
The man, who is not a member of police staff, has been released on bail.
Officers investigating the circumstances surrounding a police officer's claim to have witnessed an incident in Downing Street in September 2012 have arrested a man on suspicion of intentionally encouraging or assisting the commission of an indictable offence on or around 14 December 2012.
The 23-year-old was arrested at his home address at 20:00hrs last night, Wednesday, 19 December and questioned at a London police station. He was released on bail this morning, Thursday, 20 December, to return on a date in January 2013.
The 23-year-old - who is the second man to be arrested - is not a police officer or member of police staff.
Britain's most senior police officer has promised a "ruthless" investigation into an alleged conspiracy against Andrew Mitchell.
Andrew Mitchell has written a piece in which he has accused the police of trying to destroy his career in a smear campaign.
Police investigating the row involving Andrew Mitchell have arrested a second man today. See how the "plebgate" events unfolded.