More than 1,000 doctors have written to MPs to demand they vote against 'unsafe' assisted dying laws.
In an open letter, doctors from across the NHS warned the Terminally Ill Adults (End of Life) Bill poses a 'real threat to both patients and the medical workforce'.
The Bill aims to allow terminally ill adults in England and Wales - with less than six months to live - to legally end their lives.
But, while the doctors said it was 'entirely appropriate to have a national debate on how to address the issue of end-of-live care', they added the Bill 'is not the answer'.
They said the 'deeply flawed' legislation, which is being spearheaded by Labour MP Kim Leadbeater, is 'simply not safe'.
Their concerns about the Bill include that it will 'widen inequalities' and 'provide inadequate safeguards'.
The proposed legislation 'does not protect against the risk of coercion, particularly for women and the elderly', the letter added.
The Bill is set to return to the House of Commons for debate this Friday, with MPs expected to consider further amendments.
The Terminally Ill Adults (End of Life) Bill, being spearheaded by Labour's Kim Leadbeater, aims to allow terminally ill adults in England and Wales to legally end their lives.
In an open letter to MPs, doctors from across the NHS warned the Terminally Ill Adults (End of Life) Bill poses a 'real threat to both patients and the medical workforce'.
Campaigners in favour of assisted dying laws gathered outside Parliament ahead of MPs' latest debate last month.
Those opposed to the Bill also gathered outside the Palace of Westminster.
Campaigners opposed to the Bill recently claimed the 'momentum is against' Ms Leadbeater's legislation.
They highlighted how a number of MPs who previously backed the Bill last year have since withdrawn their support as it moves through its parliamentary stages.
Last month, MPs approved a change in the Bill to ensure no medics would be obliged to take part in assisted dying.
Doctors already had an opt-out but the new clause extends that to anyone, including pharmacists and social care workers.
Encouraging or assisting suicide is currently against the law in England and Wales, with a maximum jail sentence of 14 years.
In their open letter, the doctors pleaded with MPs to block the Bill at its Third Reading, which is expected later this month.
'As experienced medical professionals who regularly work with dying patients and who have reviewed the worldwide evidence on assisted dying, it is our opinion that this Bill poses a real threat to both patients and the medical workforce, and we urge you to vote against it.
'We are concerned that the private member's Bill process has not facilitated a balanced approach to the collection of evidence and input from key stakeholders including doctors, people with disabilities and other marginalised groups.
'This Bill will widen inequalities, it provides inadequate safeguards and, in our collective view, is simply not safe.
'This is the most important piece of healthcare legislation for 60 years and we urge you to listen to the doctors who would have to deliver the consequences of this deeply flawed Bill.'
Liberal Democrat leader Sir Ed Davey welcomed the doctors' letter, saying he had 'real concerns' about the pressure on those who feel a 'burden' on their families.
'I hope, as time has gone on, as the arguments have been better exposed, that MPs will switch sides and join the side that I and many MPs are on,' he told Sky News.
But Labour minister Sir Chris Bryant said he would now be voting in favour of the Bill having previously abstained.
'The Government doesn't have a formal position at all and individual members are free to choose how they vote,' he said.
'I'm not going to hide my own personal preference. I abstained on the first time round; I decided I wasn't going to vote because I wanted to hear the debate.
'I have listened to a lot of the debate. Of course, I don't want anybody to feel that they are a burden on society and that should lead them towards taking their own life.
'But I also have heard the cries of people who are absolutely miserable, and that's why I will be voting for the Bill.'
Last month, Justice Secretary Shabana Mahmood - an opponent of the Bill - warned assisted dying legislation was being rushed through Parliament with too little time for proper scrutiny.
In an historic vote in November, the Commons voted in favour of the Bill at its Second Reading and sent it for line-by-line scrutiny by the committee of MPs.
But Ms Leadbeater subsequently sparked anger when she made a major change to the Bill from when it was first introduced to Parliament.
It had initially been said assisted dying applications would only be allowed with the approval of two doctors and a High Court judge.
But Ms Leadbeater later proposed scrapping the High Court oversight in favour of an assisted dying commissioner and expert panels.
Under her new plans, the panels will feature a senior legal figure, a psychiatrist and a social worker who will decide on assisted dying applications.
While Friday is expected to see debate on further amendments to the Bill, it is thought a vote on the overall legislation might not take place until the following Friday, June 20.