The Metropolitan Police force says a member of the diplomatic protection group was detained Saturday on suspicion of misconduct in a public office.
It says the arrest is related to how internal police information "was obtained by national newspapers following an incident at Downing Street in September."
Andrew Mitchell was accused of abusing police officers with expletives and derogatory remarks about working class people after they tried to stop him riding his bicycle through the Downing St. gates on Sept. 19.
Mitchell denied he called an officer a "pleb," but later resigned.
The force says the arrested officer was not involved in the incident.