Pressure grows on Andrew Mitchell to resign over comments to police PRESSURE was mounting on Conservative Chief Whip Andrew Mitchell to resign today over allegations he used the term "pleb" in a foul-mouthed tirade at Downing Street police. Andrew Mitchell denies using the word "pleb" in row with police Newspaper reports police logbooks contain contradict MP's version The incident was first reported in a newspaper last Thursday, but an ongoing dispute over the words used has ensured that the story remains firmly in the news agenda, with some now calling for the Tory MP to resign. Last week Paul McKeever, head of the Police Federation, questioned whether Mr Mitchell could remain in office. "It is hard to fathom how someone who holds the police in such contempt could be allowed to hold a public office," he said. Mr Mitchell's half-hearted apology for the comments made whilst leaving Downing Street will do little to build bridges with the police who feel they have once again been treated with a lack of respect and civility by members of this government. Today 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. "Clearly Mr Mitchell is denying using certain words, effectively now impugning the integrity of the police officers," he told Sky News. 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. Liberal Democrat leader Nick Clegg, interviewed by BBC Radio 4"s Today programme from his party's conference in Brighton, said: "He challenges the way some of the words have been attributed to him. I am not going to give a running textual analysis but I think the fact that Andrew Mitchell has been as clear as he has that he is contrite about this, that he knows what he did was wrong, that he has apologised and the police officer in return has accepted the apology is important. Asked if it was time to "move on," he said: "I cannot give a running commentary on what was and was not said in an incident where I was not there."