David Cameron is under pressure to "urgently" review evidence around Chief Whip Andrew Mitchell's alleged foul-mouthed outburst at Downing Street police officers.

The Prime Minister was told by Labour to "get to the truth". Cameron was also told by the widower of murdered police officer Sharon Beshenivsky to take responsibility for Mitchell's behaviour.

Police suggested Mitchell – who is facing calls for his resignation – was close to being arrested after allegedly shouting "learn your f*****g place" and calling officers "plebs" when he was stopped from cycling out of Downing Street's main gates.

Although the former shadow police minister has apologised, he has denied using some of the language reported.

Tory Nick de Bois warned that Mitchell is in "deep trouble" if evidence emerges supporting the officers' version of events.

Shadow police minister David Hanson said: "The Prime Minister needs to review urgently Andrew Mitchell's version of events versus what the police officers have said.

"I'm asking for the PM to look at it, talk to Andrew Mitchell, clarify what he said. There will be clear evidence available, CCTV evidence, that could establish the truth."

John Tully, chairman of the Metropolitan Police Federation, said there was a written account of the incident in the notebooks of the officers from the Scotland Yard Diplomatic Protection Group.

He said: "He should resign. As a Cabinet minister it's unacceptable for someone of his standing to use such disrespectful and abusive language to a police constable."

Cameron dodged questions about whether he planned to sack Mitchell and condemned his behaviour as "wrong" and "inappropriate".

LibDem president Tim Farron said the comments, as reported, were "beyond unacceptable".

He said: "If he said what it is reported he said, it is absolutely appalling. All of us can have grouchy moments and say things we regret but it reveals, what he is reported to have said, something not terribly pleasant.

"Having said that, a lot of this stuff is still yet to be revealed. It is David Cameron's job to discipline his minister."

Ken Clarke, minister without portfolio, and senior Tory backbencher David Ruffley defended Mitchell.

Clarke said: "I have known Andrew for a long time and he is a perfectly reasonable, courteous man with the same high regard for the police services as anyone else. He obviously had a flare of bad temper on this occasion and has rightly apologised. This should be allowed to set the matter at rest."

Ruffley said: "Nothing that may have occurred this week should affect his well-deserved reputation for being on the side of policemen and policewomen."

Mitchell made his apology in a statement.

The MP for Sutton Coldfield said: "On Wednesday night I attempted to leave Downing Street via the main gate, something I have been allowed to do many times before.

"I was told that I was not allowed to leave that way. While I do not accept that I used any of the words that have been reported, I accept I did not treat the police with the respect they deserve.

"I have seen the supervising sergeant and apologised, and will also apologise to the police officer involved."

Mitchell, a keen cyclist, was reported to also have called the police "morons".

"Best you learn your f*****g place. You don't run this f*****g government. You're f*****g plebs," he was reported as saying.