The UK will cross a "legal and ethical Rubicon" if Parliament votes to let terminally ill patients end their lives, the Archbishop of Canterbury warned, as he urged MPs to reject plans to allow assisted suicide.
The Most Rev Justin Welby and heads of Christian, Jewish, Muslim and Sikh groups have issued a joint letter to every MP asking them to oppose the Assisted Dying Bill, which will be debated in the Commons on Friday (local time).
The Bill would allow doctors to prescribe a lethal dose to terminally ill patients judged to have six months or less to live and who request it.
Currently, assisted suicide is illegal under the Suicide Act 1961 and is punishable by up to 14 years in prison.
Writing in the Observer newspaper, the archbishop said he and other faith leaders had spoken out because they believe changing the law would have "detrimental effects" on society.
"A change in the law to permit assisted suicide would cross a fundamental legal and ethical Rubicon," he said.
"This respect for the lives of others goes to the heart of both our criminal and human rights laws and ought not to be abandoned.
"While it is not a crime in the UK for someone to take his or her own life, we recognise that it is a tragedy and we, rightly, do all that we can to prevent suicide.
"The Assisted Dying Bill requires us to turn this stance on its head, not merely legitimising suicide, but actively supporting it."
Mr Welby said asking to sanction doctors to take part in a person's bid to end their own life would be "a change of monumental proportions both in the law and in the role of doctors".