Grandfather Eric Mann made no secret of the fact he took the drug to help overcome the painful condition.

But a judge at Swansea Crown Court today jailed him, saying that he had not tried enough other legal treatments before taking the drug.

Mr Mann, who formerly worked at Pembroke Dock, told Swansea Crown Court that he suffered from painful and crippling arthritis which had forced him to give up work.

He said that he took cannabis to help relieve the condition, and that the pain had eased considerably.

Mr Mann denied growing and possessing the drug, on the grounds that he had a right to prevent the arthritis deteriorating.

But the judge jailed Mr Mann for a year. He was found guilty of a similar offence in 1987.

The illegal use of cannabis to help relieve conditions like arthritis, multiple sclerosis and cancer is controverisal, with many sufferers saying it does help to ease pain.

The government recently gave permission for cannabis to undergo laboratory tests, to see if it could ever be licensed as a medicine.

Meanwhile, Labour MP Paul Flynn has begun a renewed effort to get Parliament to approve the use of cannabis on medical grounds.

He describes the present law as "barbaric" and said the government was being "callous" in ignoring the pain of people who could benefit from the drug. His 10-minute rule bill will go before the House of Commons on Wednesday.