The Metropolitan Police has also announced that a second officer has been dismissed following their involvement in the 'plebgate' scandal.
James Glanville, who was a serving PC in the Diplomatic Protection Group, was arrested in January last year. He was later told he would face no criminal action but the police watchdog (IPCC) and the force agreed their was a case to answer for gross misconduct.
Granville was not on duty at the time of the 'plebgate' incident, but investigations found that later that evening he passed information about the incident to the Sun newspaper.
He later provided the newspaper a photo of PC Toby Rowland's email that he sent to his supervisors, which he got from another colleague who had been on duty at Downing Street that night. He subsequently lied about his actions in statements given to detectives from the Alice team.
A police officer who was jailed for 12 months after pleading guilty to a charge of misconduct in public office over the 'plebgate' scandal has been dismissed by the Metropolitan Police.
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.
A former policeman at the centre of the "plebgate" row has said officers on duty at the gates of Downing Street have been "betrayed" by their Metropolitan Police bosses.
Ian Richardson said he believes his colleagues' claims that Andrew Mitchell called officers "plebs" and was "officious and rude", in an interview with The Times.
Despite not hearing the exchange, Mr Richardson said Pc Toby Rowland, the officer who claims he was sworn at by Mr Mitchell, immediately recounted what was allegedly said.
Mitchell, the Conservative MP for Sutton Coldfield, admits swearing at the officers but maintains that he did not use the other words attributed.
Mr Richardson accused the Metropolitan Police of failing the officers involved by concentrating on who leaked the story to the media rather than investigating what had happened and issuing a statement to clarify the incident.
The former officer, who retired with 30 years' service in October 2012, said Mr Mitchell should not have lost his job over a "quirky incident that should have blown over".
Former Cabinet minister Andrew Mitchell has told ITV News that the IPCC report into the 'plebgate' row was an "important report" as he reiterated his gratitude to the police watchdog following the sentencing of a police officer over the affair.
He said: "I think the IPCC report is an important report and I've issued a statement about that in which, on behalf of myself and my family, I've said how grateful we are both to the IPCC and of course to Channel 4 and Dispatches who originally broke this story."
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."
In a victim impact statement, former chief whip Andrew Mitchell told of his "acute demoralisation and sense of isolation" leading up to his resignation over the 'Plebgate' affair.
He described being "devastated" to learn of Pc Keith Wallis' email to his deputy John Randall and said it led to a "very difficult" conversation with Prime Minister David Cameron: "During which he told me that he had seen the email and that I would have to go."
I protested my innocence and after a tense conversation lasting around six minutes he [David Cameron] agreed to instigate an investigation through Cabinet Secretary, Sir Jeremy Heywood.
As I understand it, Sir Jeremy's investigation revealed that Mr Wallis's email was not a reliable basis on which to sack me from the Cabinet because of inconsistencies within it.
The story continued to roll in the media for many days, during which I slowly lost the support of many Parliamentary colleagues.
Speaking after Pc Keith Wallis was jailed for 12 months for lying about witnessing the incident, Andrew Mitchell warned "this can happen to anyone."
"After nearly a year and a half my family and I are grateful to the IPCC for their statement issued today," Mr Mitchell said. "We are also very grateful to Channel 4 Dispatches for their role in exposing what happened. This whole sorry affair has been immensely damaging to everyone involved."
He added: "But above all it serves as a warning that if this can happen to a Cabinet Minister it can happen to anyone in Britain today."
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".
Pc Wallis's actions have clearly fallen way below the standards that me, my fellow police officers and the public demand.
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.
Yesterday I apologised personally to Mr Mitchell that an MPS officer clearly lied about seeing him behaving in a certain manner.
Today, I apologise to the public for Pc Wallis's behaviour.
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.