Former chief whip Andrew Mitchell has said he is pleased "justice has been done" after a police officer who falsely claimed to have witnessed the Plebgate row pleaded guilty at the Old Bailey.
Pc Keith Wallis, 53, of West Drayton, west London, admitted misconduct in public office between September 19 and December 16 2012, by saying that he had witnessed the incident.
He was charged after he sent an email to Conservative deputy chief whip John Randall, who was his MP, wrongly claiming that he had seen what happened in Downing Street on September 19, 2012.
A row erupted when then-chief whip Mr Mitchell became involved in a heated confrontation with another police officer, Toby Rowland, after he was refused permission to cycle through the main gate.
Mr Mitchell admitted swearing but denied Pc Rowland's claim that he used the word ''pleb''.
Today, the Tory MP for Sutton Coldfield welcomed Wallis's guilty plea but said the police officer's behaviour was "very sad and worrying".
He said in a statement: "I am pleased that justice has been done in a criminal court today.
"It is very sad and worrying for all of us that a serving police officer should have behaved in this way. There remain many questions unanswered; in particular why Pc Wallis wrote this email and who else was involved in this process.
"I am looking forward to seeing justice done in the up to 10 other related disciplinary cases involving police officers so that I can focus all my energy on delivering for my constituents and help David Cameron win a Conservative majority at the 2015 election."
Wallis, wearing a black suit and tie, stood in the dock and spoke only to confirm his name and that he understood the charge before entering his guilty plea.
The court heard that Wallis, who is from the Metropolitan Police Diplomatic Protection Group, admitted the offence in police interview and offered to resign.
Mr Justice Sweeney adjourned sentencing to February 6 pending pre-sentence psychiatric reports.
He released Wallis on unconditional bail but warned him that "all sentencing options remain open to the court".
Last month the Police Federation confirmed that the officer at the centre of the row was to sue Mr Mitchell.
Pc Toby Rowland issued a letter of claim for libel against Mr Mitchell relating to the issue in the wake of their differing accounts of the heated confrontation in Downing Street.
Prosecutors have found there was insufficient evidence to charge Pc Rowland with any criminal offence after the row, and Scotland Yard has said he will not face disciplinary action.
Mr Mitchell previously said he hoped the officer would give evidence on oath as part of the libel proceedings against the Sun newspaper. But Mr Rowland said he stood by his account of what was said.
Keith Vaz, chair of the Home Affairs Select Committee, which has held several evidence sessions on the Plebgate affair, said: " This plea is not only the first public acknowledgement that Mr Mitchell has been the subject of gross unfairness but it also an admission that a criminal offence has been committed against him.
"With 11 other officers being subject to misconduct hearings, and the further investigation by the IPCC, this appears to be a complete vindication of Mr Mitchell's position.
"Bernard Hogan-Howe, the Metropolitan Police Commissioner, told the Home Affairs Select Committee that he would await the outcome of the criminal proceedings, as well as misconduct hearings, before making any statement. I welcome his apology to Mr Mitchell, which is the right thing to do.
"Taken with the apologies of the other Chief Constables, it shows that the internal mechanisms of the police have not worked on this occasion. Lessons have to be learnt in order to restore full public confidence in way these matters are dealt with.
"Now is the time to turn the page on this whole unfortunate incident, which took only 45 seconds but has cost the taxpayer hundreds of thousands of pounds, Mr Mitchell his job and damaged the reputation of the police."
Met Police Commissioner, Sir Bernard Hogan-Howe apologised to Mr Mitchell and said Wallis' behaviour "falls way below the standards expected" of his officers.
He said: "This investigation has been a ruthless search for the truth as at the heart of this are extremely damaging allegations that officers have lied and falsified statements against a Cabinet minister.
"The evidence against Pc Wallis was such that he has entered a guilty plea. To lie about witnessing something and provide a false account falls way below the standards that I and Pc Wallis' colleague expect of police officers. His actions have also negatively impacted upon public trust and confidence in the integrity of police officers.
"I would also like to apologise to Mr Mitchell that an MPS officer clearly lied about seeing him behaving in a certain manner. I will be writing to him offering to meet and apologise in person.
"I expect my officers to serve the public without fear or favour, where officers break the law they must expect to be held to account and answer for what they have done.
"As there are still a number of gross misconduct hearings I must take great care not to say or do anything that prejudices the outcome of those very important hearings as these officers have important questions to answer."