Tory Chief Whip Andrew Mitchell has re-iterated his apology for his tirade against police at the gates of Downing Street last week.

Mr Mitchell denied calling a police officer a "pleb" during the altercation.

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, 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."