Funding has been approved for one of the first ever clinical trials using cannabis extract to relieve multiple sclerosis (MS) symptoms.

The study, officially sanctioned by the UK Medical Research Council (MRC) and led by Dr John Zajicek of Derriford Hospital in Plymouth, can now start recruiting more than 600 patients with the crippling disease.

The MRC is providing a grant of �950,000 to carry out the research.

Patients will be recruited from MS clinics around the country - anyone wishing to take part should contact their own specialist.

The research will examine whether any active ingredient of cannabis can help lessen the muscular rigidity which characterises the disease.

But a full licenced treatment is still unlikely to be available inside two years.

Peter Cardy, chief executive of the MS Society of Great Britain, said: "It is clearly an unacceptable state of affairs when many people suffering from a serious medical condition feel driven to break the law.

"The trial will provide us with the evidence we need to know whether cannabis is a safe and effective treatment."

Patients taking part will be given one of three treatments - either an extract of all the ingredients of cannabis, tetrahydrocannibol, thought to be the principal active chemicals, or simply a dummy treatment.

The drugs will be administered in the form of pills, not smoked.

The Derriford study is not the only one planned - Dr Anita Holdcroft from Hammersmith Hospital in London is planning to use the drug to see if it can alleviate post-operative pain.

No cure

Approximately 85,000 people in the UK suffer from MS, for which there is still no cure.

It is a progressive condition affecting the nervous system which leads to loss of motor function in the limbs, and eventually death in many cases.