Former Health Secretary Patricia Hewitt will lead demands for a law change to protect those who help terminally-ill relatives and friends travel abroad for an assisted suicide.

Ms Hewitt said today she had tabled an amendment, supported by MPs from all sides of the Commons, to the Government's Coroners and Justice Bill to protect such individuals from prosecution.

Although it is designed to provoke debate and is not expected to be pushed to a vote, the move sparked immediate condemnation from opponents of assisted suicide who warned it would lead to "an opening of the floodgates".

A number of high-profile cases have put the issue firmly in the spotlight and more than 100 MPs have signed a Commons motion calling for it to be debated.

Paralysed rugby player Daniel James, 23, committed suicide at a clinic run by Dignitas in September last year - leading the Crown Prosecution Service to consider charges against his parents.

Mark and Julie James, from Sinton Green, Worcester, made payments to Swiss clinic Dignitas, sent documents and made travel arrangements to take their son to Switzerland.

But the Director of Public Prosecutions said that although there was enough evidence to pursue charges, and a reasonable chance of securing a conviction, such a prosecution would not be in the public interest.

Last month, multiple sclerosis sufferer Debbie Purdy lost an Appeal Court bid to secure a guarantee from the DPP that no such charges would be brought if she took advantage of a foreign clinic.

She wants to be sure that if her suffering becomes intolerable, her husband, Cuban violinist Omar Puente, will not be prosecuted if he helps her travel abroad to die in a country where assisted suicide is legal.

But three judges ruled Ms Purdy was not legally entitled to the kind of specific guidance she was seeking.

Ms Hewitt said: "In the long term we need a Bill to change the law to allow terminally ill, mentally competent adults suffering at the end of their lives the choice of an assisted death, within safeguards, in this country.

"In the meantime, I hope that the amendment I have tabled will prompt the long overdue parliamentary debate necessary to bring the law on assisted suicide in line with the practice of the Director of Public Prosecutions, and the courts."

Her amendment, which bears the signatures of MPs from all three major parties, would mean that any act "done solely or principally for the purpose of enabling or assisting (an individual) to travel to a country or territory in which assisted dying is lawful" would not be treated as "encouraging or assisting" suicide.

It is set to be debated when the Bill returns to the main chamber of the Commons for its Report Stage debate on Monday and Tuesday.

Sarah Wootton, chief executive of the Dignity in Dying group, said: "Currently the Coroners and Justice Bill fails to distinguish between maliciously encouraging a suicide and compassionately assisting a terminally ill, mentally competent adult who wants to die.

"Clearly the law should protect vulnerable people from abuse, but at the same time it should not criminalise people who accompany those who make rational decisions to end their suffering.

"The Director of Public Prosecutions and the Courts have made public their reluctance not to prosecute those who accompany loved ones abroad, when they have chosen to have an assisted death in a country where it is legal. The amendment aims to ensure that the law reflects this practice."

But the Care Not Killing alliance said relaxing the law could lead to abuses.

Director Peter Saunders said: "The Government is, commendably, trying to protect vulnerable people by tightening up the Suicide Act to outlaw internet websites that encourage suicide.

"And yet here we have the euthanasia lobby trying, at the same time and in the same Bill, to encourage suicide by removing any risk of prosecution for anyone assisting someone to go abroad for euthanasia or assisted suicide.

The result would be a law that discouraged suicide with one hand and encouraged it with the other. That would be farcical as well as tragic."

Dr Saunders said the recent high-profile cases were of people "seriously determined" to go abroad to commit suicide but removing legal safeguards could dangerously extend the practice.

He pointed out that the Appeal Court in the Purdy case risked exposing British citizens to "the very worst laws anywhere in the world" by turning a "rare exception" into a rule.

"The law has an important deterrent effect and that means the cases we see are those involving resolute and self-confident people who haven't been coerced. But take away that deterrent and we would soon start to see cases of abuse and an opening of the floodgates," he said.

"I hope and trust that MPs will be on their guard next week and see this amendment for what it really is: a cynical and disingenuous attempt to force the legalisation of assisted dying here."