David Cameron has resisted demands for an inquiry into the conduct of Tory Chief Whip Andrew Mitchell as the row over his tirade against police officers in Downing Street deepened.
Mr Mitchell sought to draw a line under the affair as he appeared before the cameras for the first time to apologise publicly for his outburst after officers refused to allow him to cycle through the main gates.
However, police representatives reacted with fury after he made clear he did not accept reports that he called the officers "plebs" in the course of the altercation on Wednesday evening.
The chairman of the Metropolitan Police Federation John Tully said he was effectively accusing the officers involved of lying and called on the Prime Minister to institute an inquiry.
Earlier The Sun, which broke the story, reported that it had now seen a police report of the incident which indicated that Mr Mitchell did call the officers "plebs" as well as swearing at them repeatedly.
The report, drawn up for senior officers, was said to be backed up by at least two officers making the same verbatim note of the exchange in their pocket books.
Arriving in Whitehall for a hastily arranged "doorstep" with reporters, Mr Mitchell accepted he had not shown sufficient respect to the police and reiterated the apology he issued last week after details of the encounter first emerged, saying: "I didn't show the police the amount of respect I should have done. We should all respect the police, they do an incredibly difficult job."
However, when he was pressed on whether he used the politically explosive word "plebs", he said: "I want to make it absolutely clear that I did not use the words that have been attributed to me," a claim which Mr Tully said put him directly at odds with the account given by the officers, casting doubts on their honesty.
Chief Superintendent Irene Curtis, president-elect of the Police Superintendents' Association, added: "By saying he disputes what the officer has said, he's actually calling into question the police officer's integrity, and for a police officer that's a very serious matter."
Downing Street indicated that, in the absence of an official complaint from Scotland Yard, Mr Cameron did not see the need to take the matter any further.