A potential assisted dying law for England and Wales would have “clear criteria, safeguards and protections”, the MP behind a new Bill has insisted in the face of concerns about a so-called “slippery slope” to take in people who are at risk of feeling pressured to end their lives.

Only those who are terminally ill would be eligible under the Bill, it has been confirmed, amid calls from some campaigners for those enduring unbearable suffering to come within the scope of a new law.

The formal short title of Labour MP Kim Leadbeater’s legislation for choice at the end of life is the Terminally Ill Adults (End of Life) Bill.

Dignity in Dying campaigners in Parliament Square in support of an assisted dying bill

Dignity in Dying campaigners gathered in Parliament Square in support of the new Bill (Lucy North/PA)

The Spen Valley MP will formally introduce her Bill in the House of Commons on Wednesday, and it is expected to be debated and face a first vote on November 29.

The detail of the proposed legislation is unlikely to be set out until closer to that debate, with Ms Leadbeater saying she is speaking to doctors and lawyers as well as campaigners on all sides to “make sure we get this right”.

Archbishop of Canterbury Justin Welby has warned of his concerns around introducing any form of legislation for assisted dying.

He told the BBC: “I think this approach is both dangerous and sets us in a direction which is even more dangerous, and in every other place where it’s been done, has led to a slippery slope.”

The Archbishop of Canterbury Justin Welby The Archbishop of Canterbury Justin Welby has warned of his concerns around legislation for assisted dying (Doug Peters/PA)

But Ms Leadbeater has rejected this argument.

She told ITV’s Good Morning Britain she would not have such concerns so long as “we get this legislation right”, adding: “That’s why the next six weeks and the debates that will come in the following months are really important.

“We’ve got the benefit in this country of looking at what other countries have done. And I’m very clear, based on what I’ve seen so far and the research that I’ve done is, if we get this right from the start, which some places have done, places like Oregon and certain states in Australia, we have very strict criteria, then those jurisdictions do not broaden out the criteria.

“So we have to get it right from the start with very clear criteria, safeguards and protections.

“And I’m not looking at the model that is going on in Canada. I’m looking at those other jurisdictions where this is done well and in some cases it’s been done for a long time, very well, and the criteria have never been extended.”

The Canadian model is open to people experiencing intolerable suffering caused by their medical condition, whereas in Oregon it is limited to those who are terminally ill.

The long title of the proposed legislation, which would apply to England and Wales, is a “Bill to allow adults who are terminally ill, subject to safeguards and protections, to request and be provided with assistance to end their own life”.

If the Bill clears its first hurdle at the end of November, it will face line-by-line examination in committee and further Commons votes before being sent to the Lords where the process begins again, meaning any change in the law would not be agreed until next year at the earliest.

It is possible that MPs could vote against it on November 29, as they did last time changes to the law were considered in 2015, preventing it going any further.

Ms Leadbeater has indicated she would like to see a “time frame” on the diagnosis of patients, and she told BBC’s Newsnight there must be both medical and judicial safeguarding when it was put to her that the Bill could require two medical professionals and a judge to agree.

High-profile supporters of legalising assisted dying include Dame Esther Rantzen who is terminally ill and has pleaded with the public to write to their MPs to ask for “the right to choose, not to shorten our lives, but to shorten our deaths”.

MPs will have a free vote in Parliament, deciding according to their conscience rather than along party lines.

Prime Minister Sir Keir Starmer has previously supported assisted dying and made a personal promise to Dame Esther to make time for a debate and vote on the issue.

Members of Distant Voices, Christian Concern, the Christian Medical Fellowship and SPUC gathered in Westminster to protest against the proposed legislation Members of Distant Voices, Christian Concern, the Christian Medical Fellowship and SPUC gathered in Westminster to protest against the proposed legislation (Lucy North/PA)

Trevor Moore, chairman of campaign group My Death, My Decision, said he had hoped the new Bill would “represent the first step in a profound and compassionate shift in how we provide the dignity of choice for people who are intolerably suffering”.

Actor and disability campaigner Liz Carr, speaking before the Bill’s formal title was announced, said limiting the legislation to the terminally ill would not lessen her fears about its potential consequences for vulnerable people.

She told the PA news agency: “Neither (the Bill being limited to terminally ill or being wider) allay my fears, neither make me feel less worried.

“Because I know this is such a concerted campaign and such a push, and there are huge lobbyists nationally, internationally to change these laws that I just don’t feel reassured because they want what they want, and what they want is to legalise assisted suicide.”

Campaigners both for and against the proposed new law gathered outside Parliament on Wednesday.