A police officer has been criticised by a judge for his "cack-handed" attempt to stop young people smoking on a late-night bus.

Pc John Ellis, based at Bicester traffic department, told a court he took cigarettes from two young women on the last bus from Oxford back to Bicester.

It was alleged during a trial that Pc Ellis, who was off duty and had been drinking, aggressively confronted a number of young people who were ignoring a smoking ban.

The officer, 30, of Avocet Way, Bicester, was charged with assaulting Shelley Haynes, 18, by kicking her in the abdomen, after an argument on the bus escalated in the early hours of January 10, this year. Pc Ellis denied common assault, and said his behaviour had not been aggressive.

He was found not guilty by District Judge Stuart Miller, who heard several prosecution witnesses give differing accounts during a five-day trial at Newbury Magistrates' Court.

However, the judge said Pc Ellis should have asked the bus driver to deal with the smoking issue, and said his conduct fell far short of the standards expected of a police officer. The judge said: "Mr Ellis took a cack-handed and clumsy approach."

Miss Haynes, who had been for a night out with friends at The Studio nightclub, in Oxford, told the court she had consumed about eight bottles of alcopops.

She said a man, allegedly Pc Ellis, grabbed her hand and snatched the cigarette from it, before stamping it out on the floor.

She said he briefly showed his police badge but did not give his name or full details.

She said: "He grabbed hold of my wrist and threw me back down into my seat."

She said he then kicked her in the lower part of the stomach, and tried to kick her again but she blocked it with her foot.

Pc Ellis said he did not deliberately kick Miss Haynes, but he could have accidentally caught her when someone behind him got him in a neck lock and pulled him down between two seats, he said.

He received bruising to the side of his face from a punch in the melee, he said.

Pc Ellis said he had consumed five pints of Guinness and three other alcoholic drinks during the evening, but was in control of himself.

His manager, Insp Steve Bridges, said the allegations against Pc Ellis were "completely out of character".

Miss Haynes' friend Scott Edwards, 18, who had drunk about 10 bottles of lager that evening, said he stood up and placed himself between Miss Haynes and Pc Ellis after the officer had walked to the end of the bus to challenge her. But he did not see her being kicked.