Multiple sclerosis patients could be driven to suicide by a lack of access to treatment, a campaigner will tell MPs.
Debbie Purdy says that guidance on assisted suicide issued in 2009 is being "undermined" because the quality of life of MS sufferers 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.
Ms Purdy is trying to get a drug called Sativex, which helps relieve spasms caused by the disease, on the NHS.
The four anti-spasmodics routinely prescribed by her local health trust cause her 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 MS Society says it is also because National Institute for Health and Clinical Excellence (Nice) guidelines on MS have not been updated since 2003, and there are geographical inconsistencies because funding decisions are made by local health trusts.
