Plot thickens as police call for resignation after Mitchell disputes officer's version

Andrew Mitchell's attempt to draw a line under his foul-mouthed rant at a Downing Street policeman appeared to backfire yesterday as he was accused of impugning the integrity of the police and more allegations emerged of his high-handed treatment of civil servants.

In his first public appearance since the altercation became public, the Tory Chief Whip said he wanted to apologise for not showing the police the "amount of respect" they deserved – but insisted he did not "use the words" that had been attributed to him.

His denial that he had called the Downing Street protection officers "plebs" enraged rank-and-file police.

"Mr Mitchell is effectively now impugning the integrity of the police officers," John Tully, chairman of the Metropolitan Police Federation, said. "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."

Last night the Cabinet Secretary Sir Jeremy Heywood refused to conduct an investigation into the confrontation – despite calls from Labour to do so.In a letter to shadow home secretary Yvette Cooper, Sir Jeremy wrote: "In light of the apology given, and also the fact that the officer concerned has accepted the apology and does not wish to pursue the matter further, the Metropolitan Commissioner reiterated that no further action would be taken. Given these circumstances neither the Prime Minister nor I see any purpose in a further investigation."

The Prime Minister expressed his confidence in Mr Mitchell but it also emerged yesterday that senior officials in the Department for International Relations, where he worked before the reshuffle, had privately raised concerns about his behaviour. Mr Mitchell is said to have told his Permanent Secretary that he expected male officials in his department to wear jackets and ties at all times and wanted to be addressed as "Secretary of State".

Despite his clothing diktats, Mr Mitchell himself was said to sometimes hold meetings in his office without any shoes and still wearing his bicycle clips.

"He could be cantankerous and aggressive," said one official. "He was a horrible person to do business with." A spokesperson for the Department said there had never been "any formal complaint" against Mr Mitchell from anyone in the Department.

Scotland Yard is investigating how The Sun came to see police statements detailing officers' accounts of their confrontation with Andrew Mitchell.

Yesterday the paper published details of the contemporaneous notes taken by the police officers. The constable said Mr Mitchell told him: "Best you learn your f**king place. You don't run this f**king government. You're f**king plebs."

A Metropolitan spokeswoman said: "We are aware of this. The Directorate of Professional Standards has been informed. Inquiries into the circumstances are being carried out."

The Sun yesterday said it had seen a police report of the incident prepared for senior officers which was backed up by at least two officers making the same verbatim note of the exchange in their pocket books. A spokesman for The Sun said the investigation into how they got the story appeared to be a case of trying to shoot the messenger.