The number of terminally ill people going abroad to end their lives will rise unless the law banning assisted suicide in Britain is changed, the Lords were told yesterday.

A Bill allowing a terminally ill adult to choose medical help to die, within strict safeguards, was introduced by Lord Joffe, a crossbencher who said the present law was out of tune with majority opinion and was a cause of "profound and unnecessary suffering to many people".

The move has reignited the right-to-die debate, with the head of the ethics forum at the Royal College of Nursing backing the Bill, but Catholic bishops and disability groups urging peers to reject it.

Lord Joffe, opening the second reading on his private member's Bill, said much had changed since the issue was looked at a decade ago. Government policy was out of date. People with terminal illnesses could go to Switzerland for assisted suicide outside legal safeguards and the Netherlands, Belgium and the American state of Oregon had assisted-suicide legislation with no evidence of abuse.

The present law stipulated a jail term of 14 years for aiding or abetting a suicide, which put patients at risk of making "spontaneous and ill-informed decisions to end their lives" and carried "grave risks" for doctors who ignored the law out of compassion. "Finally, it results in patients leaving the United Kingdom to die lonely deaths in Zurich and perhaps elsewhere without any safeguards," Lord Joffe said.

Research from other countries, he estimated, showed 8,000 were helped to die with their consent each year and 18,000 without. Yet there was only a handful of prosecutions, "which demonstrates there is a large gap between what the law says and what happens".

The Bill was opposed by Lord St John of Fawsley, a Tory former cabinet minister, who said elderly and sick people often felt they were a burden on relations. "Once euthanasia is a possibility they would be constantly asking themselves whether they should avail themselves of this option," he said. "Legalised euthanasia is a short cut offering facile solutions to problems of the highest complexity." Relief from pain was important to the dying but even more important was the need to "assuage the inner misery and loneliness of the dying patient".