The police officer at the centre of the "plebgate" row is seeking damages from former Chief Whip Andrew Mitchell of up to £200,000.
PC Toby Rowland is suing Mr Mitchell for suggesting the officer was not telling the truth about the dispute at the gates of Downing Street in 2012.
Mr Mitchell was accused of swearing at police and calling them 'plebs'.
The Conservative MP denies the allegations but resigned as chief whip in the wake of the controversy.
High Court documents show that lawyers for PC Rowland justify the claim on the grounds that his reputation has been damaged by Mr Mitchell's remarks and he suffered "great distress, humiliation and upset".
Conservative MP David Davis, the former shadow home secretary, said it is clear that former chief whip Andrew Mitchell has suffered an injustice an "all that remains is for him to go back into Cabinet."
Metropolitan Police officer Keith Wallis, who was today sentenced to 12 months in jail for lying about witnessing the infamous 'Plegate' incident involving Andrew Mitchell, wrote a drunken email to his MP falsely claiming that the former chief whip shouted "You ******* plebes" at officers.
Mr Mitchell said in a victim impact statement: "The existence of the emails contributed to my acute demoralisation and sense of isolation. They were therefore a contributory factor in the events which led to my resignation."
The Independent Police Complaints Commission (IPCC) has criticised "collusion" between officers involved in the 'plebgate' row.
Speaking after Pc Keith Wallis was jailed for 12 months for lying about witnessing the incident, the body's head Deborah Glass said: "The patchwork of evidence from emails, text messages and telephone calls does not suggest an organised conspiracy to bring down a Cabinet Minister.
"But there was clearly collusion between certain officers to, as they saw it, blow the whistle on bad behaviour toward one of their own, which ultimately had the same effect."
She added: "The actions of Pc Wallis - and the other officers responsible for turning a largely inaudible altercation lasting less than a minute into a national scandal - have not only caused injustice to Mr Mitchell, they have brought shame upon the police service.
"Now that the criminal proceedings have concluded it is important for the Metropolitan Police Service to proceed as quickly as possible to the misconduct hearings and to deal effectively with any underlying issues so that they can finally close the book on this sorry chapter."
Britain's most senior police officer, speaking after the sentencing of Pc Keith Wallis, said that the officer - who is one year away from retirement - would now be the subject of a misconduct process "as soon as possible".
Two officers from the DPG have received final written warnings and a third officer has undergone management action in relation to inappropriate comments, the Met confirmed.
Wallis, along with four other officers from DPG, will be the subject of gross misconduct hearings due to start at the end of the month.
A Metropolitan Police officer has been jailed for 12 months after pleading guilty to a charge of misconduct in public office over the "plebgate" scandal last month.
Pc Keith Wallis, 53, falsely claimed in an email that he had witnessed an incident in Downing Street involving the former Chief Whip Andrew Mitchell and other officers in September 2012.
Former Chief Whip Andrew Mitchell wrote an impact statement ahead of Pc Keith Wallis' sentencing for misconduct in public office over the "plebgate" scandal.
The Sun's Political Editor Tom Newton Dunn, who broke the original 'plebgate' story, has claimed the police officer's admission today to falsifying witnessing the row, was merely "a red herring to the main event": the Downing Street PC who alleged Andrew Mitchell called him a "pleb".
A Sun spokesman said: "We stand by our story and will defend Mr Mitchell's claim vigorously".
Mr Mitchell is suing the paper for libel.
In a statement, he said: "I am pleased that justice has been done in a criminal court today....I am looking forward to seeing justice done in the up to 10 other related disciplinary cases involving police officers"
Former Chief Whip Andrew Mitchell was in his constituency after a police officer admitted to falsely claiming to have witnessed the 'plebgate' row.
He had earlier issued a statement saying: "It is very sad and worrying for all of us that a serving police officer should have behaved in this way."
David Cameron said it was "completely unacceptable" for a police officer to falsify their account of an incident after PC Keith Wallis pleaded guilty to misconduct in public office over the "plebgate" affair.
The Prime Minister said: “It is completely unacceptable for a serving police officer to falsify an account of any incident.
"Andrew Mitchell has consistently denied the version of events presented in the email and I welcome the fact that the officer concerned has now pleaded guilty.”