Debbie Purdy is concerned her husband could be prosecuted
Former health secretary Patricia Hewitt is urging MPs to change the law to allow people to take terminally ill patients abroad for assisted suicide.
The Labour MP has tabled an amendment to the Coroners and Justice Bill which would protect them from prosecution.
The amendment which may be debated but not voted on at this stage, is not thought to have much chance of success.
Care Not Killing, which opposes assisted suicide, said the effect of Ms Hewitt's amendment would be "tragic".
BBC political correspondent Ben Wright said the government did not plan to change the law and the amendment, which has been signed by a handful of Labour, Conservative and Lib Dem MPs, was unlikely to pass.
More than 100 MPs have signed a Commons motion calling for the issue to be debated.
Downing Street said that while Gordon Brown did not favour a change in the law, Labour MPs would be given a free vote if there was a division on Ms Hewitt's amendment next week.
Ms Hewitt told the BBC she had been "troubled" by the issue for years and was aware more than 700 Britons were members of Dignitas and may choose an assisted suicide in future.
She said her amendment was only "reinforcing the current prosecution policy".
But if she got the chance in the future to introduce a private members' bill she would like a specific law to allow people who are terminally ill but "mentally competent" the choice of an assisted death.
In October multiple sclerosis patient Debbie Purdy, from Bradford, West Yorkshire, lost a High Court case in which she tried to clarify the law on assisted suicide.
She wanted a guarantee from the Director of Public Prosecutions (DPP) that her husband would not be prosecuted for murder if he assisted her death in Swiss euthanasia clinic Dignitas.
But two senior judges ruled the current guidelines were adequate. The Appeal Court said it had to be Parliament which decided if the law should change.
Since Dignitas opened in 1998, more than 100 British citizens have ended their lives in Switzerland, where it is legal to aid and abet a suicide, provided it has not been carried out for a profit.
Lesley Close: "Palliative care can't affect matters of dignity"
It is illegal in the UK and anyone convicted faces up to 14 years in prison.
While there have been no prosecutions of relatives to date, the DPP has carried out investigations into cases.
At the end of last year, the parents of 23-year-old Daniel James, who was paralysed in a rugby accident, were told they would not face charges over his death.
He ended his life in Switzerland in September even though he was not terminally ill.
Director of Public Prosecutions Keir Starmer QC said while there was "sufficient evidence" to prosecute the couple, their "fiercely independent son" had not been influenced by his parents and so charging them would not be in the public interest.
Liberal Democrat peer Lord Carlile said the current system should be left broadly as it is and the law was actually "quite clear".
"There is a law against assisting suicide and there is also an important constitutional discretion which can be exercised so that a prosecution may not be brought if it is in the public interest not to bring it," he said.
Making the law "prescriptive" would make using that discretion more difficult, he said.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.