Labour questioned the future of Government chief whip Andrew Mitchell in the wake of a reported foul-mouthed rant at Downing Street police officers.
Shadow home secretary Yvette Cooper called on the Government to clarify what was said during the altercation which occurred when Mr Mitchell tried to cycle out of Downing Street on Wednesday.
Reports in The Sun suggest the 56-year-old chief whip called the officers "plebs", telling them to "learn your f****** place" after he was stopped from using the main gate. The Tory MP, who was appointed to the post by David Cameron in the recent reshuffle, denied using the reported language but apologised to the officers for not treating them with proper respect.
But Ms Cooper said this was not good enough, dubbing the reported outburst an "utter disgrace", and questioned how Mr Mitchell could do the job of chief whip if he could not keep his temper in check.
She said: "These are appalling reports. No one should treat police officers or public servants in this way. And the idea that a Cabinet minister could behave like this towards police officers doing their job is an utter disgrace. It tells you all you need to know about this out-of-touch Government and its attitude to public servants.
"Downing Street clearly have a lot of questions to answer. They must make clear exactly what happened, including what was said and whether the deeply offensive language reported was used. How can a chief whip hope to do his job or instil respect when he behaves like this and can't even keep his cool?"
Millionaire Mr Mitchell on Thursday night denied using the language but apologised to the officers. The MP for Sutton Coldfield, who was also a minister under John Major in the early 1990s, apologised in a statement.
He 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."
Mr Mitchell, a keen cyclist, was reported by The Sun to also have called the police "morons". It reported him as saying: "Best you learn your f****** place. You don't run this f****** Government. You're f****** plebs."
A spokeswoman for No 10 said the Prime Minister is aware of the outburst, "is glad that Mitchell has apologised" and added that police "should always be treated with respect".