A coalition of over 40 organisations has warned of the "dangers" for terminally ill and disabled people if assisted suicide is made legal.
Responding to comments this week by Labour leader Sir Keir Starmer in favour of changing the law, Care Not Killing said this would put pressure on people to end their lives prematurely.
Dr Gordon Macdonald, Chief Executive of Care Not Killing, said that current laws "do not need changing".
"Changing the law to legalise assisted suicide and euthanasia in the UK would represent a dramatic change in how doctors and nurses treat and care for people and put the lives of the vulnerable, terminally ill and disabled people at risk," he said.
"Indeed, these dangers are particularly acute when the health service is crumbling, hospices are underfunded and one in every four people who would benefit from palliative can't access it."
Care Not Killing is a broad alliance of human rights and disability rights organisations, health care and palliative care groups, and faith-based organisations groups committed to better palliative care and opposing efforts to change the law on assisted suicide.
The coalition predicts that legalising assisted suicide will lead to an increase in overall suicide rates.
Dr Macdonald continued: "Sir Keir needs to recognise the real dangers associated with legalising state sanctioned killing, such as the pressure it puts on people to end their lives prematurely, and the growing body of evidence showing assisted suicide appears normalises suicide in the general populations.
"Indeed, academics who looked at this emerging trend concluded that legalising assisted suicide in Oregon was associated with an increase of 6.3 per cent in the numbers of suicides, once all other factors had been controlled. Among over 65s the figure was more than double that.
"If this was repeated here in the UK that would mean hundreds of more suicides every single year."
The last time Westminster voted on legalising assisted suicide was in 2015, when it was defeated.
Sir Keir has promised to give MPs another vote on the issue if Labour wins the next general election.
A Commons report last month suggested that the law on assisted suicide is likely to change in parts of the British Isles soon, with Jersey, a Crown Dependency, expected to be first. Scotland and the Isle of Man are also considering changes to the law.
The report from the parliamentary Health and Social Care Committee said that UK ministers must consider the implications of legal divergence on the matter.
