ANDREW Mitchell's future in the Coalition Government was hanging by a thread last night after his meeting with police officers failed to quell the growing chorus of demands that he resign or be sacked.

The embattled Chief Whip met representatives of the Police Federation for 45 minutes in the hope of drawing a line under the continuing dispute over his foul-mouthed rant at Downing Street officers; it is now three weeks since the incident happened. However, the meeting seemed to have simply intensified calls for him to go.

Ken Mackaill, Chairman of West Mercia Police Federation, made clear Mr Mitchell now had "no option but to resign" after refusing to say what words he did use to the police on duty. The Cabinet minister has apologised and insists he did not use the word "plebs" but has so far declined to say what he actually did say.

"He refused to tell us what he did say on the grounds he did not want to impugn police officers' integrity and start, I quote the word, a 'firefight' with police. Unfortunately, that is exactly what happened: the question of integrity remains unresolved," said Mr Mackaill, who was accompanied at the meeting by the secretaries of the West Midlands and Warwickshire federations.

He added: "This is about the honesty and accuracy of police records and there are implications for officers giving evidence in court, after all. We take the view that this is a Cabinet minister, challenging the accuracy of police records and that is of interest to all police officers."

Mr Mitchell, who was said to have been "tense" and "upset" when challenged over whether the Downing Street officer in question was lying, left the meeting in his Sutton Coldfield constituency without commenting.

Earlier, Yvette Cooper, the Shadow Home Secretary, said it was time for the Cabinet Minister to go. "This has gone on long enough. Neither the Prime Minister nor the Chief Whip has proved capable of coming clean swiftly and putting this right. David Cameron needs to put an end to this now and remove Andrew Mitchell from his position."

Tory MPs have privately made their views known that they have lost faith in Mr Mitchell; a poll during the Conservative Party conference showed the Chief Whip had a net rating among Tory activists of -74%.

At Westminster, which returns from recess on Monday, there is an increasing feeling that Mr Mitchell's position is becoming untenable given he will find it increasingly hard to instil party discipline among already truculent Tory backbenchers.