Lord David Cameron has become the first former UK prime minister to give his backing to moves to legalise assisted dying for terminally-ill adults.

The Conservative former PM, who was ennobled by Rishi Sunak and served as his foreign secretary, had previously opposed moves to change the law.

But in an article for the Times newspaper, he said he had been won over to supporting in the Terminally Ill Adults (End of Life) Bill, set to be debated by MPs on Friday.

Writing for the Times, Lord Cameron said: “As campaigners have convincingly argued, this proposal is not about ending life, it is about shortening death.

“Many of these safeguards will be familiar from previous proposals. But this new Bill protects the vulnerable still further, including by making coercion a criminal offence.”

Former prime ministers Liz Truss, Boris Johnson, Baroness Theresa May and Gordon Brown have all said they are opposed to the Bill.

None of them will have a vote on Friday, but Baroness May and Lord Cameron would if the Bill reached the Lords.

“If this Bill makes it to the House of Lords, I will be voting for it,” Lord Cameron said.

In changing his mind, Lord Cameron said he had considered whether there were sufficient safeguards to protect vulnerable people, and said he believed there were.

He also suggested he did not agree with arguments the Bill could be a “slippery slope” to further reforms.

Justice Secretary Shabana Mahmood shared her belief the law change could lead to “death on demand” when she made clear her opposition.

But Lord Cameron said that “‘Thin end of the wedge’ arguments can be used against almost every proposal for social change”.

He added: “I would urge MPs to engage with the substance of the proposal in front of them.

“I believe that there are strong arguments for suggesting that it is a sensible and practical resting place for public policy in this area.”

The Tory peer also said he did not find arguments the Bill would put unnecessary pressure on the NHS convincing.

He said his final consideration had been whether the law change would “lead to a meaningful reduction in human suffering”.

“I find it very hard to argue that the answer to this question is anything other than ‘yes’,” he said.

This proposal is not about ending life, it is about shortening death

Lord Cameron and his predecessor Mr Brown both lost children at a young age, but have come to very different conclusions about the Bill.

During his time as opposition leader in 2009, Lord Cameron’s son Ivan died aged six, after suffering from a form of epilepsy.

Mr Brown – then the prime minister – cancelled their weekly exchange at the despatch box out of respect.

Writing in the Guardian last week, the former Labour prime minister shared how the death of his daughter Jennifer at 11 days old had informed his opposition to the Bill.

Mr Brown described that period as “among the most precious days” of his and his wife Sarah’s lives.

He said he believed better palliative care, rather than assisted dying, was needed for improved end-of-life support.