THE father of a 14-year-old pupil expelled from King's School at Canterbury for smoking cannabis has described the decision as grossly unfair.

Timothy Lyons said that although Eton had been criticised for its tough drugs policy, its treatment of Prince Harry in similar circumstances was "positively enlightened" compared to the way his son had been treated.

Toby Lyons was excluded from one of the country's leading private schools after testing positive for cannabis in a school drugs test.

Mr Lyons, who runs a London fund management company, said Toby had admitted smoking four joints at a party during school holidays one week before the drugs test, but had never smoked or possessed the drug at school.

"Prince Harry made a similar mistake," said Mr Lyons. "His father treated him in a sensible way, discouraging him but not punishing him severely. Eton supported Prince Charles, as did the Queen, the Prime Minister and the Home Secretary. Yet King's School has forced my son to leave the school. It is grossly unfair and lacks common sense."

Mr Lyons, from Lamberhurst, near Tunbridge Wells, said head teacher Canon Keith Wilkinson refused to accept that the school's drugs policy was random and indiscriminate and that such tests could not provide an accurate measurement of cannabis use.

The father stressed: "In a letter the head teacher told me 'there was no evidence that Toby did not use drugs while at school'.

"I was astounded at this statement and pointed out that similarly, there was no evidence that he or other members of the school had not used them either.

"Cannabis smoking is not to be condoned but nor is it the end of the world. It is not considered the plague on the world it was once thought to be and alcohol is at least as dangerous."

Canon Wilkinson said school rules prevented him discussing an individual pupil. He said one or two pupils had been excluded from King's every year for the past two or three years for smoking cannabis. He denied that King's had a knee-jerk attitude towards cannabis and said that, to have a knee-jerk reaction one would have to deviate from a policy.

"We have applied our policy consistently and compassionately," he added. "We believe proscribed drugs are harmful to an individual's development and we aim to put into effect measures that prevent and deter pupils being involved in what could be a damaging activity."