Proposed new laws to allow terminally ill patients to end their lives are "utterly inadequate" and pose a risk to public safety, according to a former president of the High Court's family division.
Baroness Butler-Sloss warned safeguards contained in the Assisted Dying Bill offered vulnerable people "no real protection" from pressure or coercion by others and would put them in greater danger than the current law.
The Bill, which is to be debated by MPs in the Commons on Friday, 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.
Baroness Butler-Sloss, in a letter to the Times, said: "The attempted safeguards contained in the Assisted Dying Bill are utterly inadequate and will not protect vulnerable individuals. I have serious concerns that the Bill, if passed, presents significant public safety risks.
"In my opinion, this Bill would place many elderly, ill or vulnerable people in significantly more danger than the current law.
"My experience of presiding over the family division of the High Court showed me again and again how subtle and calculated the pressure, coercion and even control exerted on a vulnerable individual can be."
Judges were not "well placed" to decide whether a person had been coerced within the two week time limit for decisions, the cross-bench peer added.
Baroness Butler-Sloss's intervention follows calls from the Archbishop of Canterbury for the legislation to be rejected.
But former director of public prosecutions Keir Starmer, writing in the Times, said the medical and legal safeguards outlined in the Bill were "robust".
Mr Starmer, who helped devise prosecution guidelines on assisted suicide, said: "There is no case for limiting that assistance to the amateur kind offered by family or the professional kind provided by Dignitas.
"The safeguards in the Assisted Dying Bill are certainly strong and robust. A person may only be provided with assistance to end their life if a High Court judge is satisfied they have a voluntary, clear, settled and informed wish to do so.
"So long as these safeguards are enshrined in law, the wish of those who want to die with dignity at home with professional medical assistance can be met without compromising protection for the vulnerable."
A poll of 10,000 Saga customers found three in five over-50s support legislation that would allow Dignitas clinics to open in the UK.