A woman with multiple sclerosis is staging a High Court challenge to clarify the law on assisted suicide.

Dignity in Dying campaigner Debbie Purdy, who has progressive multiple sclerosis, said she may at some stage wish to receive assisted suicide and wants her husband Omar to be immune from prosecution in the UK should he accompany her to Dignitas, the Swiss assisted suicide clinic.

According to Dignity in Dying, formerly known as the Voluntary Euthanasia Society, Mrs Purdy's concerns are centred on quality of life and dignity issues:

"What worries me the most about my disease is that it is degenerative," she was quoted as saying. "I don't want to be forced to make a decision about the end of my life before I am ready to stop enjoying it. I want to wait until the last minute to decide if I can bear the facing pain and indignity I am facing."

Care Not Killing said it welcomed a full airing of the arguments, but warned that legalising assisted suicide would put vulnerable people at risk and make them susceptible to exploitation and abuse, a view upheld by the House of Lords vote on Lord Joffe's assisted dying Bill in 2006.

Care Not Killing's campaign director and head of the Christian Medical Fellowship, Dr Peter Saunders said it would be unwise to change current law on assisted suicide:

"We need to be very clear on what has been agreed here. The High Court Judges have simply granted permission for Debbie Purdy to have a full hearing in court but have made it very clear that they are not giving her any grounds for optimism that her arguments will succeed.

"We welcome this opportunity to revisit the arguments and are confident that the court will find that, in order to protect vulnerable people from exploitation, the current law should be upheld."

Under current law, assisting in another's suicide is a criminal offence which carries a sentence of up to 14 years imprisonment.

"The law is very clear on this matter and should not be changed. Changing it to allow assisted suicide would place vulnerable people - the sick, elderly, depressed and disabled - under pressure, whether real or imagined, to request early death," said Dr Saunders

"Vulnerable people often feel that they constitute a financial or emotional burden to others and the so-called 'right to die' can so easily become the duty to die. Once a person has been 'helped to die' it is often very difficult to know whether there has been subtle coercion involved from someone who has an interest in a person's death."

Dr Saunders went on to call for better palliative care of seriously ill people.

"There are over 70,000 people in Britain with multiple sclerosis at present and only a very small number ever request assisted suicide. These requests are virtually never persistent if patients' physical, emotional and spiritual needs are properly addressed.

"Our key priority must therefore be to make the very best palliative care more widely accessible and to get rid of the postcode lottery of care that currently exists in Britain," he said.

"The key issue here remains whether the law should be changed for the very small number of people who press for assisted suicide. Our view is that in order to protect others from exploitation it should not be."

Purdy's legal challenge comes several years after the late Diane Pretty, a sufferer of motor neurone disease, failed in her high profile bid to make assisted suicide legal.