A Sussex man who has motor neurone disease today helped to deliver a 'right-to-die' petition at Downing Street.

John Howard, 48, from Worthing, was one of four terminally-ill people joining Brian Pretty, whose late wife Diane lost her court fight for the right to commit assisted suicide.

The petition - begun by Mrs Pretty - includes 40,000 signatures and another 10,000 names collected via the internet.

Supporters at the Voluntary Euthanasia Society claimed it would be the largest online petition ever handed in to Prime Minister Tony Blair.

Mr Howard, a father-of-four and a former training manager, said thousands of terminally ill people would like the option to be able to choose medical help to die.

He said: "We're asking MPs and MSPs from all parties to act now by supporting a change in the law."

The other campaigners joining Mr Pretty and Mr Howard were Steve Barksby, 51, from Manchester, who has Aids; Lisa Cook, 34, from Huddersfield, who has the gene which causes Huntingdon's disease; and Jane MacDonald, 53, from north London, who has cancer and multiple sclerosis.

Motor neurone disease sufferer Mrs Pretty, 43, from Luton, lost a lengthy legal battle to allow Brian to help her commit suicide.

She always said she wanted him to help her end her life because she feared the choking and asphyxia often caused by her disease.

Her arguments were rejected by the European Court of Human Rights less than a fortnight before she died.

Mr Pretty said after her death on May 11: "Diane had to go through the one thing she had foreseen and was afraid of - and there was nothing I could do to help."

A campaign web site - www.ukActNow.org - was also due to go live today to help publicise the case for assisted suicide.

Anti-euthanasia campaigners say such a change in the law could endanger terminally-ill people, forcing them into opting for assisted suicide because they feel they are a burden on relatives.