Frank Field, the former Labour MP for Birkenhead, has revealed that he is terminally ill as he backed a law that would allow assisted dying.

Field, 79, represented the Merseyside constituency for almost 40 years, before forming his own party and losing the seat in the 2019 general election. He was later made a crossbench peer, taking on the title Lord Field of Birkenhead.

During a Lords debate on the assisted dying bill, which would allow terminally ill adults in England and Wales to legally seek support to end their lives, a statement was read out on behalf of Field by Baroness Molly Meacher, who is leading the bill.

“Our colleague Lord Field of Birkenhead, who is dying, asked me to read out a short statement,” Baroness Meacher said, adding that the contents may come as a surprise to members in the chamber.

The statement confirmed that Field is dying and that his own experience and that of colleagues had led him to change his mind on assisted dying and to support the bill.

The statement from Field said: “I’ve just spent a period in a hospice and I’m not well enough to participate in today’s debate. If I had been, I would have spoken strongly in favour of the second reading [of the bill].

“I changed my mind on assisted dying when an MP friend was dying of cancer and wanted to die early, before the full horror effects set in, but was denied this opportunity.

“A major argument against the bill is unfounded. It is thought by some the culture would change and people would be pressured into ending their lives.

“The numbers of assisted deaths in the US and Australia remains very low, under 1%, and a former supreme court judge in Victoria, Australia, about pressure from relatives, said: ‘It just hasn’t been an issue’. I hope the house will today vote for the assisted dying bill.”

Field represented Birkenhead from 1979 to 2019, making him one of the longest-serving MPs in the Commons.

The assisted dying bill, tabled by Meacher, proposes that only terminally ill patients with full mental capacity, and who are not expected to live more than six months, would be eligible to apply for an assisted death.

Campaigners argue that a change in the law would give those at the end of their lives greater control over how and when they die, while opponents say it could leave vulnerable people exposed to unwanted pressure.

The archbishop of Canterbury has said that although safeguards in the legislation are stronger than in previous attempts to change the law, they still do not go far enough.

“What we want is assisted living, not assisted dying. There is no difference between us in compassion. It is our concern about the effectiveness of the safeguards and the care for the vulnerable,” he told BBC Breakfast.

“Sadly people make mistakes in their diagnosis. It leaves people open to very, very intangible forms of coercion and pressure … The point is, we have to have compassion for the vulnerable.”

Previous attempts introduce similar laws have all been defeated. The issue is being debated on Friday in parliament for the first time in more than six years.

Opening the debate, Baroness Meacher said “a great deal” had changed since then, notably a “radical shift” in the views of doctors. She earlier told BBC Radio 4’s Today programme: “The fact is that there has been a most extraordinary shift in medical opinion over the last five years.

“Five years ago, all the royal colleges were against assisted dying. Now one after another, the Royal College of Physicians ended their opposition in 2019, only last month the BMA [British Medical Association] ended their opposition, these organisations do undertake surveys of their members.”

She added: “It is interesting that the religious leaders do not in any way represent the people of faith, who describe themselves as religious, 80% of them want assisted dying.”

A recent YouGov poll showed 73% of the public supported doctor-assisted dying for people who are terminally ill, compared with one in three MPs.

The former Scottish secretary Michael Forsyth, who had previously opposed assisted dying, is one of a number of politicians who have changed their position on the issue in recent years. He told the Today programme of going to see his father, who had terminal cancer and was in “very great pain”, before he died.

“I said to him, ‘Dad, I am so sorry you are in this position’, and he completely took me aback by saying ‘you are to blame’. And I said, ‘how am I to blame?’ and he said, ‘because you and others have consistently voted against the right to die’. I would like to be relieved of this, and they can’t relieve me of the pain, and I am in this position because of folk like you’.”

The bill, which is now having its second reading in the Lords, is unlikely to become law without government support.