A third attempt to legalise assisted suicide will be launched at Holyrood on Monday, after a cross-party group of politicians backed changing the law to give the teminally ill the right to a "dignified death".

Liam McArthur, the Lib Dem MSP, is to bring forward a members bill which if passed would allow adult Scottish residents who are terminally ill and mentally competent to access life-ending drugs, with the permission of two doctors.

Two previous attempts to legislate to allow people with incurable conditions to end their lives early in Scotland have failed, most recently in 2015 when proposals were voted down by 82 votes to 36.

However, those in support of a change in the law claim public opinion is now firmly behind reform. Those against the plans said that they would be "vigorously opposed".

In an open letter, a cross-party group of 12 MSPs, including former Scottish Tory leader Jackson Carlaw, said that people who were dying should have the right "to have a good death at a time that is right for them".

Mr McArthur was among the MSPs that backed proposed legislation in 2015, when there was a free vote on the issue.

"I have long believed that dying Scots should be able to access safe and compassionate assisted dying if they choose, rather than endure a prolonged and painful death," he said.

"The current blanket ban on such assistance is unjust and causes needless suffering for so many dying people and their families across Scotland.

"If you have reached the limits of palliative care and face a bad death, none of the current options available to you in Scotland represents an acceptable alternative to a peaceful, dignified death at home."

He claimed that 87 per cent of Scots now backed allowing assisted dying, although religious groups will campaign against a change in the law.

Currently, anyone who helps someone end their life in Scotland could theoretically face charges of culpable homicide or murder, depending on the circumstances of the case.

In a 2016 ruling, Scotland’s most senior judge said it was not a crime to "assist" someone to take their life but that an act that was the “immediate and direct cause of the person’s death” would be criminal.

Mr McArthur’s bill is being lodged at Holyrood on Monday, and a consultation is planned for the autumn.

Opponents claim that even with safeguards in place, people could feel pressured to end their lives early for financial reasons or because they feared becoming a burden on loved ones.

Gordon Macdonald, chief executive of the Care Not Killing Alliance, which opposes assisted suicide, said: "It was only a few years ago that the Scottish Parliament overwhelmingly rejected the last bill because MSPs realised that it is just not safe to legalise assisted suicide or euthanasia.

"In every place where state assisted dying has been legalised we see those who are vulnerable, elderly or the disabled being put under pressure to end their lives or at risk of abuse.

"The promised safeguards don’t work, are routinely flouted and often are removed very quickly as laws get extended to include those who are not terminally ill or psychiatrically unwell."