Sir Terry Pratchett travelled to Switzerland to see a British man dying

Sir Terry Pratchett defends assisted suicide film Jeremy Paxman challenges Pratchett on the issue of assisted suicide.

In the film shown on Monday, the 63-year-old author - who has Alzheimer's disease - travelled to Switzerland to see a British man dying.

Liz Carr, a disability campaigner, said she thought the documentary was pro-suicide propaganda and said she was surprised the BBC had made it.

But Sir Terry said: "I believe it should be possible for someone stricken with a serious and ultimately fatal illness to choose to die peacefully with medical help, rather than suffer."

The BBC denied the screening could lead to copycat suicides and said it would enable viewers to make up their own minds on the subject.

Ms Carr said: "I and many other disabled older and terminally ill people, are quite fearful of what legalising assisted suicide would do and mean and those arguments aren't being debated, teased out, the safeguards aren't being looked at.

The Bishop of Exeter, the Right Reverend Michael Langrish, said: "I want to see much more emphasis put on supporting people in living, than assisting them in dying."

He said: "The law still enshrines that sense of the intrinsic value of life. But the law ultimately is not there to constrain individual choice. It's there to constrain third party action and complicity in another person's death.

"That remains illegal. There may be ameliorating circumstances that can be taken into account. But the law remains clear and is there to protect the vulnerable."

Debbie Purdy, who has multiple sclerosis, went to court to protect her husband from prosecution if he accompanies her to the Dignitas clinic in Switzerland.

"Lawyers and judges have been the only people who have been prepared to defend my rights... and my right to life and the quality of my life is the most important thing to me."

The programme, which was aired on Monday on BBC Two, showed Mr Smedley travelling from his home in Guernsey to Switzerland and taking a lethal dose of barbiturates at the Dignitas clinic.

She said: "It clearly didn't seek to hide the realities of assisted dying. In setting out one person's views on assisted dying, it challenges all of us to think about this important issue head on and ask what choices we might want for ourselves and our loved ones at the end of life."

She said the current legal situation in the UK meant "not only are people travelling abroad to die, but there are also those who are ending their lives at home, behind closed doors, or with the help of doctors and loved ones who are helping illegally."

But Alistair Thompson, a spokesman for the Care Not Killing Alliance pressure group, said: "This is pro-assisted suicide propaganda loosely dressed up as a documentary."

Campaigners claim it is the fifth programme on the subject produced by the BBC in three years presented by a pro-euthanasia campaigner or sympathiser.

The BBC denied it was biased on the issue and a spokeswoman said the documentary was "about one person's experience, Terry's journey exploring the issues and the experience he is going through".