A former police officer at the centre of the Plebgate affair is suing Andrew Mitchell MP over comments he made in the media surrounding the controversy.
Toby Rowland was the policeman on duty guarding the gate in Downing Street when Mitchell tried to leave through the vehicular exit on his bicycle.
Mitchell himself has launched his own libel bid against The Sun over the disputed events in September 2012.
Rowland is being backed by the Police Federation which released a short statement earlier today: “We can confirm that Pc Toby Rowland yesterday issued a letter of claim for libel against Andrew Mitchell MP. This relates to comments he made following the media-termed Plebgate incident in Downing Street in 2012.
"It would be inappropriate to comment further at this time while there are ongoing legal issues."
Rowland told Mitchell that he could not cycle through the main Downing Street gate and would instead have to dismount and pass through the pedestrian exit.
At this stage, Rowland claims Mitchell because abusive and said: “You should know your f****** place, you don't run this f****** Government, you're f****** plebs."
However, the MP insists he said: ''I thought you guys were supposed to f****** help us''.
Prosecutors found that there was insufficient evidence to charge Rowland with any criminal offence after the row, and Scotland Yard said he will not face disciplinary action.
Last week Mitchell said he hoped the officer would give evidence on oath as part of the libel proceedings against the Sun newspaper.
''I have told the truth about this incident. The police did not. My reputation was destroyed. I was vilified, relentlessly,'' he said.
The MP told Channel 4 News: ''What I do know is that I was stitched up; I was fitted up in Downing Street by armed police officers whose sole duty is to defend officials and to defend Downing Street.''
''We believe that the CCTV shows that the account of Pc Toby Rowland is at very best inaccurate.
''I never said these phrases… no-one speaks like that these days. It's like a Hooray Henry, a lout from a 1920s B-movie being sort of characterised."
But Rowland said he stood by his account of what was said.
The Police Federation spokesman added: "The Federation has supported Pc Rowland with the provision of legal advice in respect of this matter. All subscribed members of the Police Federation are entitled to such support for legal representation as they see fit.
"Such applications are considered carfeully by the Federation and then passed on to legal representatives to consider the legitimacy of any case before a decision is made on any such legal proceedings. That has been done in this case."
MP David Davis, a close political ally of Mitchell, said: "We have been trying to get Pc Toby Rowland into the witness box to face the evidence and cross-examination under oath, and if this law suit by any means accelerates that, so be it."