Former Cabinet minister and Sutton Coldfield MP Andrew Mitchell must accept the verdict of the High Court on the "Plebgate" libel action and move on, David Cameron has said.
The Prime Minister insisted it was "never right to be abusive or rude" to a police officer and said the judge had "made very clear his verdict".
Mr Justice Mitting decided that the former chief whip did call Pc Toby Rowland a "pleb" because the officer did not have the "wit, imagination or inclination" to invent it.
Asked about the outcome of the case after he made a keynote speech in Staffordshire on immigration, Mr Cameron said: "On the issue of Andrew Mitchell, I mean, let me be clear - it is never right to be abusive or rude to a police officer. I think that is extremely important.
"But, look, we've had a court case now. That's how we do things in this country.
"The judge has made very clear his verdict and I think everyone should accept that verdict and move on."
Mr Justice Mitting said he had reached the "firm conclusion" that the 58-year-old MP used the "politically-toxic" word "pleb" in Downing Street in September 2012 when he was not allowed to cycle through the main vehicle gates.
Mr Mitchell, who resigned as whip a month after the altercation, vehemently denied this during his two-week libel action against News Group Newspapers.
The police officer at the centre of the Plebgate row has said the "pain" of going through the courts "has been indescribable" after a judge found in his favour over Andrew Mitchell.
Speaking outside the High Court, PC Toby Rowland said he had "huge regret" that "what happened at the gates of Downing Street more than two years ago ended up here".
He said he and his team had tried "everything possible" to avoid court action.
"I am delighted that here again my innocence, integrity and reputation as a police officer has been recognised," he added.
PC Rowland also called for a "line to be drawn" over the incident.
The overall costs of Andrew Mitchell's failed 'Plebgate' libel battle have been put at £3 million, court sources have told the Press Association.
Former Government chief whip Andrew Mitchell has said he is "bitterly disappointed" to have lost his High Court libel action over the "Plebgate" incident.
Speaking outside the High Court, Mr Mitchell said the verdict came after a "miserable two years".
The MP, who has been ordered to pay interim costs of £300,000, said he now wanted to "bring this matter to a close and and get on with our lives".
After the ruling PC Toby Rowland said he hoped a "line can be drawn and everyone can be left in peace".
Former Government chief whip Andrew Mitchell has been ordered to pay interim costs of £300,000 after he lost his High Court libel action over the "Plebgate" incident.
The Police Federation of England and Wales has said it is "pleased" Mr Justice Mitting has ruled in PC Toby Rowland's favour after Andrew Mitchell lost his High Court libel action over the "Plebgate incident".
Toby's name has been cleared and his integrity restored. Toby has conducted himself with dignity and professionalism in relation to this incident and subsequent inquiries and legal cases.
It is important that this incident is now brought to a close to allow Toby and his family to look to the future.
PC Rowland sued Andrew Mitchell for libel over statements accusing him of fabricating the alleged verbal abuse at Downing Street in 2012.
Former government chief whip Mitchell lost his libel action against News Group Newspapers over The Sun's reporting of the "Plebgate" incident.
Andrew Mitchell would have avoided the personally and financially devastating verdict in his High Court libel action if he had shown a "scintilla of humility", his fellow Conservative MP Michael Fabricant has tweeted.
This is a personal tragedy for Andrew Mitchell which needn't have happened if only he had sown a scintilla of humility. #plebgate
If Andrew Mitchell had shown some humility, said he had lost his temper and not sure what he'd said, but was sorry - he'd still be in Gov't.
The police officer in the Plebgate incident lacked the "wit, imagination or inclination" to make up the exchange with Andrew Mitchell, Mr Justice Mitting has said.
The judge's ruling rejected the allegation there was collusion by the officers on the Downing Street gate following the row with the then-chief whip.
Mr Justice Mitting said PC Rowland was "not the sort of man who would have had the wit, imagination or inclination to invent on the spur of the moment an account of what a senior politician had said to him in temper".
Andrew Mitchell looked "grim-faced" throughout the verdict as he learned he had lost his 'Plebgate' libel action, ITV News Political Correspondent Carl Dinnen has tweeted.
PC Rowland impassive throughout the #plebgate verdict. Andrew Mitchell, with his family and David Davis, grim-faced three rows further back.
PC Toby Rowland claimed statements made Mr Mitchell from December 2012 onwards falsely suggested he had fabricated his allegations.
Mr Mitchell had denied saying: "Best you learn your f****** place - you don't run this f****** government - you're f****** plebs."
He said he would never call a policeman a pleb "let alone a f****** pleb" - although he agreed he muttered audibly under his breath 'I thought you lot were supposed to f****** help us' - but not at the officer.
The 58-year-old MP for Sutton Coldfield resigned as whip a month after the altercation.
The judge at London's High Court has said he is "satisfied" Andrew Mitchell did use the "politically toxic word pleb" in the exchange with PC Toby Rowland at the Downing Street gates.
ITV News Political Correspondent Carl Dinnen relayed Mr Justice Mitting's words from court, tweeting:
#Plebgate Judge; I am satisfied heat Mr Mitchell did say the words alleged or at least something close to them....
#Plebgate Judge; Mitchell too angry to remember what he said. PC Rowland too unimaginative to make it up. Mitchell probably said 'Pleb'
Mr Mitchell sued News Group Newspapers (NGN) over a September 2012 story in The Sun that claimed the then-chief whip had a branded police officer a "f****** bleb" for not allowing him to cycle through the Downing Street gate.
NGN based its report, which it said was substantially true, on the account given in his log by PC Toby Rowland.