David Cameron said it was "very important" the investigation into the 'plebgate' affair was "thoroughly carried out and proper answers are delivered".
The Metropolitan Police said the allegations against the officer arrested today are "extremely serious" and the investigation continues with "urgency, determination and an open mind."
The latest information from Scotland Yard reveals there are now six officers and one civilian arrested or being investigated over the Andrew Mitchell "plebgate" incident.
The man arrested over alleged leaks to the media linked to the "plebgate" affair was not one of the officers at Downing Street during the incident in September 2012, the Metropolitan Police said in a statement.
A police officer responsible for protecting Government officials has been arrested over alleged leaks to the media about the "plebgate" incident.
The 46-year-old from the Diplomatic Protection Group was held at his work place in central London on suspicion of misconduct in public office.