Tory Chief Whip Andrew Mitchell has denied calling a police officer a "pleb" during an altercation in Downing Street.

Mr Mitchell reiterated his apology after not showing the police "the amount of respect I should have done" during the confrontation last week. But asked if he called the officer a "pleb", he said: "I want to make it absolutely clear that I did not use the words attributed to me."

Questioned by reporters as he arrived for work in Whitehall, Mr Mitchell refused to be drawn on what he actually said to the officer. "I have apologised to the police, I have apologised to the police officer involved on the gate and he's accepted my apology and I hope very much that we can draw a line under it there," he said.

Earlier however, Deputy Prime Minister Nick Clegg stepped up the pressure, insisting that Mr Mitchell must provide a full account of what happened after The Sun reported that police logbooks showed he called officers "plebs" and swore repeatedly.

"I don't know what happened, I don't think anybody knows precisely what happened and there are rival versions being circulated in the press. I think, therefore, it's really important that Andrew Mitchell explains fully and in detail his version of events."

Mr Mitchell, who arrived in Whitehall in a VW Polo, accepted that he should not have spoken to the officers in the way that he did when they refused to allow him to take his bicycle through the main gates of Downing Street on Wednesday.

"It had been the end of a long and extremely frustrating day - not that that is any excuse at all for what happened," he said. "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 he made clear that he was determined to resist calls for his resignation, saying: "I am now going to go in and get on with my work. Thank you very much indeed."

The chairman of the Metropolitan Police Federation John Tully warned that Mr Mitchell's comments did not mark the end of the matter and called on David Cameron to hold an investigation, telling Sky News: "Clearly Mr Mitchell is denying using certain words, effectively now impugning the integrity of the police officers. I think that is very serious. I think the Prime Minister or Downing Street officials should hold an inquiry and if Mr Mitchell is proved to have lied, then he should be sacked."

According to The Sun, police logbooks show Mr Mitchell called officers "plebs" and swore repeatedly during his furious outburst. The reports, made for senior officers, detail how the Chief Whip was warned he would be arrested under the Public Order Act if he swore at the team again, the paper said. The officer who bore the brunt of the former his rant was said to have made a note within hours of the exchange after Mr Mitchell told him: "You haven't heard the last of this".