Diplomatic Protection Officer SO6 has been accused of giving the media information about then-chief whip Andrew Mitchell allegedly calling police officers "plebs".
Scotland Yard said: "The arrest is linked to previous inquiries by the Met as to how internal information was obtained by national newspapers following an incident at Downing Street in September.
"These inquiries found no evidence to suggest any of the officers involved in the incident were involved in the unauthorised release of information. The officer arrested was not on duty at the time of the incident in Downing Street."
The officer was bailed yesterday after his arrest on Saturday on "suspicion of misconduct in a public office" after fresh information was received last Thursday.
John Tully of the Met Police Federation told The Guardian: "Clearly it is of great regret that the MPS [Metropolitan Police Service] has found it necessary to take this action - I trust justice will ultimately prevail."
Mitchell has claimed that he did not use the words attributed to him, though he admitted saying to the officers on the night: "I thought you guys were supposed to f**king help us."
He has since maintained that the contents of the allegedly leaked police logbook of the incident were false.