Multiple sclerosis patients could be driven to suicide by a lack of access to treatment, a campaigner will tell MPs today.

Debbie Purdy says that guidance on assisted suicide issued in 2009 is being “undermined” because the quality of life of people with MS is being damaged by inconsistent access to medication.

The “right-to-die” campaigner, who fought for clarification of suicide laws, is set to speak at the All Party Parliamentary Group on MS.

She said: “People are making choices because their lives are unbearable. I’ve got permission to live but now we’ve got to look at what my life is.

“Now I’ve got the clarity in the law and I’m confident that my husband would not be prosecuted I want my life to be worth living.

“People are choosing to end their lives because the provision of medication and care is not suitable for that individual.”

Mrs Purdy is trying to get the drug Sativex, which helps relieve spasms caused by the disease, on the NHS.

The four anti-spasmodics routinely prescribed by her local health trust cause unpleasant side effects.

A government report published last year showed that the UK came 13th out of 14 developed countries in the amount of drugs prescribed for MS.

It said the low level was partly down to “a cautious and/or sceptical attitude among some neurologists regarding the benefits of treatment”.

The Multiple Sclerosis Society says it is also because National Institute for Health and Clinical Excellence guidelines on MS have not been updated since 2003, and there are geographical inconsistencies because funding decisions are made by local health trusts.

Ms Purdy said: “The guidelines are so out of date. Rates of MS are increasing phenomenally and we are not keeping up.

“I have had fantastic support from the medical profession. My doctors, nurses, carers, everybody in the NHS has been brilliant so I’m not kicking their commitment to finding a solution.

“It’s a national health service, it should be more consistent and the guidelines should be completely up to date. We’re not giving our doctors and nurses the correct support if they’re out of date.”

Director of policy and research for the MS Society Dr Jayne Spink said: “People with MS should have access to proven treatments, no matter where they live in the UK. Withholding the right treatment is totally unethical and can have an absolutely devastating effect on people’s lives. People with MS have the right to a full life and it’s high time that the people holding the purse strings recognised this.”

MS affects around 100,000 people in the UK.

A spokeswoman for NICE said it is currently developing guidance on Sativex, which is due to be published in January 2012.

It will publish a review on whether there is a clinical need to update MS guidelines in June this year, and is developing a range of guidance on the disease.

A Department of Health spokeswoman said: “In the absence of NICE guidance, primary care trusts make local funding decisions on individual treatments, taking into consideration all available evidence.

“Our plans to modernise the NHS will empower GPs to make these funding decisions based on clinical knowledge and an understanding of their patients’ individual needs.”