Constable Andrew Taylor, 31, denied causing actual bodily harm and was acquitted at Luton Crown Court. He justified his use of the spray, saying Kenneth Whitaker, 67, had been unco-operative, abusive and threatening.

But the judge was openly critical of the jury's verdict, saying they might have reason to "reflect" on their verdict.

Judge Daniel Rodwell QC told them: "If in future other old age pensioners are gassed or assaulted by police, they may indeed have this particular case in mind."

PC Andrew Taylor ran out of the courtroom

He refused to award PC Taylor legal costs and said the case had been "disturbing and upsetting". PC Taylor broke down and rushed from the court as the verdict was read out.

It is thought to be the first case where a policeman has appeared in court accused of misusing the incapacitant, CS spray.

The incident took place in May last year, two months after Bedfordshire Police issued its officers with CS spray.

PC Taylor, a traffic officer, spotted Mr Whitaker parked on a double yellow line, close to a roundabout in Kempston, near Bedford. He had been dropping off his disabled wife off at the hairdresser.

The officer says he had asked Mr Whitaker his name, but the pensioner refused, was threatening and abusive and twice tried to bite him.

The scene of the incident in Kempston

After giving a warning, PC Taylor used the CS spray twice in his face and Mr Whitaker, who had remained in his car wearing a seatbelt, was then arrested, handcuffed and held for nine hours.

During the trial the judge criticised the Home Office and Bedfordshire Police. He said he was alarmed that the police seemed to think the spray could be used to control someone and not just for self defence.

The spray left Mr Whitaker temporarily blinded in one eye and needing hospital treatment.

Compensation pay-out

Mr Whitaker was not in court to hear the verdict but it emerged after the hearing that he had already been paid thousands of pounds compensation by Bedfordshire police. The payment was agreed in an out of court settlement, after he took civil action against them.