LONDON (AP) — A key member of Prime Minister David Cameron's government quit Friday amid a simmering dispute over an incident last month in which he was accused of abusing police officers with foul language and derogatory remarks about working class people.

Andrew Mitchell, who was chief whip and attended Cabinet, was accused by police of confronting them angrily after they asked him to get off his bicycle to pass through gates at Downing Street, the famous road where Cameron has his official London residence.

In an official record of the confrontation on Sept. 19, a police officer insisted Mitchell had sworn and used the words "moron" and "pleb" — a pejorative term for the working class. Mitchell acknowledged he had sworn, but bitterly denied using the other words.

The "pleb" remark put new pressure on Cameron's government, particularly is it carries out billions of pounds worth of cuts to public services and welfare programs — many of which are causing hardship to ordinary Britons.

Pleb — short for plebeian — comes from the Latin plebeius, the mass of ordinary citizens apart from the elite of upper-class patricians.

Cameron's Conservative Party, which dominates the coalition government, is seen by many as elitist and lacking empathy with the poor. The leader has made huge efforts to overturn that image, but opponents point out that half the members of his Cabinet went to private schools — which educate about 7 percent of all Britons, while two-thirds are millionaires.

Mitchell was educated at the private Rugby school and had a career in banking after he served in the military and as a U.N. peacekeeper.

"I have made clear to you — and I give you my categorical assurance again — that I did not, never have and never would call a police officer a 'pleb' or a 'moron' or used any of the other pejorative descriptions attributed to me," Mitchell wrote in his resignation letter. However, he said it had been "obviously wrong of me to use such bad language."

Police have been further incensed by Mitchell's challenging of a police officer's note of the incident, suggesting that his claim that the record of what was said was wrong represented a slur on the man's professionalism.

The showdown at Downing Street happened days after two unarmed policewomen were shot dead in the city of Manchester, with public sympathy and admiration for officers riding high.

Mitchell told Cameron at meeting Friday that he felt he could no longer carry out his duties as chief whip — the government official in charge of party discipline.

Cameron, in a letter to Mitchell, said the incident in Downing Street "was not acceptable, and you were right to apologize for it." However, he praised Mitchell for his work as chief whip, and in his previous role in charge of Britain's overseas aid ministry.

Veteran lawmaker George Young, who joined Parliament in 1974, was appointed as Mitchell's replacement. Young, like Cameron, attended the elite Eton school.

In a separate embarrassing incident, Treasury chief George Osborne was accused Friday of traveling in a first class train compartment with only a standard class ticket.

Officials insisted that, though Osborne had only a lower priced ticket, he later paid an upgrade fee to a train guard.