Klaus Eckstein, a retired headmaster, is adamant that he has the right to die in the manner of his choosing. 'If I really wanted to kill myself, I could walk down to the local level-crossing and wait for the next express,' he said. 'But that would be rather messy, and very unfair on the poor train driver. There must be a better way of ending your life.'

Like hundreds of other Britons, Eckstein subscribes to Dignitas, the Zürich-based organisation that is helping foreigners to end their lives. Eckstein, 70, enjoys good health but believes that, should he fall ill, he may need the services of what is scathingly described as 'death tourism'.

It emerged last week that three British people had committed assisted suicide at Dignitas's apartment within a week. Two of them, Bob and Jenny Stokes from Bedfordshire, were invalids in wheelchairs, but neither had a terminal illness. Both were given doses of lethal barbiturates.

The news of their deaths provoked an outcry from their families, doctors and some MPs. But there exists a more general unease about the fact that people are prepared to travel abroad to die in a way which they feel will be painless and peaceful and would be considered illegal in Britain.

The work of Dignitas has again raised the subject of euthanasia, two years after a motor neurone disease sufferer, Diane Pretty, brought it into the headlines with her plea for her husband to be allowed to help her die at the right moment. The courts rejected her plea, but there is public confusion about to what extent doctors are allowed to relieve the pains of ter minal illness and how much they can help patients on their way.

A man like Eckstein feels we have no right to interfere in the decision of others to use Dignitas. 'My life is my own. It is for me to decide how and when I want to put an end to it.'

He sent a £45 registration fee to Dignitas last year and now pays an annual £10 membership fee, which gives him the right to use its service at any time. Speaking from his home in Cambridge, he said; 'If there is an organisation that can provide me with the help I need at that point, then I will use it.'

Now Lord Joffe, a former human rights lawyer, has been invited to meet officials in the Department of Health to discuss his Private Member's Bill calling for the legalisation of assisted suicides for the terminally ill. Although the Bill has no chance of becoming law unless it is supported by the Government, the fact that he has been asked for a meeting reveals that the stated position that there is no reason to change the law may be reviewed.

'The Government has made it clear that they are against any change on the issue,' Joffe said. 'But at least they are now willing to discuss it. The clear solution to this problem [of Dignitas] is changing the law, making it unnecessary for people to go abroad.'

Joffe, who will meet civil ser vants in the next fortnight, said that it was better for people to receive honest advice from their doctor about the choice of voluntary euthanasia rather than going to charities outside British government regulation.

Last November The Observer revealed that the first British patient, a 77-year-old with advanced oesophageal cancer, had travelled to Zürich with his son and daughter in order to commit suicide. After meeting Dignitas's founder, Ludwig Minelli, and explaining his reasons for wanting to die, the man went to the apartment in Zürich where, with the help of a nurse, he was given a barbiturate to swallow. Within five minutes he was in a deep coma, from which he did not recover.

Minelli asserted that the man, who was not identified, had been fully competent to make the decision when he took his life. 'Clearly he had thought about this course of action. This man was in very great fear that the illness could cause him even more pain.'

But the Stokes case has caused complications, because their relatives did not know their plans. According to the Swiss district attorney, Edwin Luscher, Jenny Stokes presented medical papers, signed by a doctor, to say that she had multiple sclerosis. But her relatives said that they were unaware that she had this disease. MS is a chronic condition, but not necessarily a terminal one.

The Voluntary Euthanasia Society, which has been campaigning for years for a change in the law, so that people who have a terminal illness and are mentally competent can be helped to die, is alarmed by the Zürich trend. Its chief executive, Deborah Annetts, said that urgent clarification of the Suicide Act of 1961 was needed to protect patients, their relatives and medical staff.

The British Medical Association argues that it is the doctor's first duty to try to cure and help patients, not to assist them to die. They also point out that palliative care in Britain is improving and that people should look to services which mean that, should they develop an incurable illness, they can be given proper pain relief.