Former chief whip Andrew Mitchell was accused of directing a heated rant towards officers at Downing Street.
A 46-year-old officer from Scotland Yard’s Diplomatic Protection Group has been arrested over alleged leaks to the media linked to the “plebgate” affair, the Metropolitan Police said.
Three weeks ago Metropolitan Police commissioner Sir Bernard Hogan-Howe said that a file of evidence on the case could be handed to prosecutors by the end of this month.
Scotland Yard said that because of “ongoing developments” no interim report had yet been submitted to the Crown Prosecution Service.
Two other men have been arrested so far. A 52-year-old PC who is also from the DPG was held on suspicion of misconduct in public office and bailed until a date in February.
A 23-year-old was arrested on suspicion of intentionally encouraging or assisting the commission of an indictable offence and also released on bail.
Four other constables in the unit, which is responsible for protecting government officials and diplomats, have been placed on restricted duty over misconduct claims.
The plebgate row began after chief whip Andrew Mitchell was accused of a heated rant against officers as he left Downing Street.
