Judges have no place deciding who can die by assisted suicide the former head of the UK High Court’s family division has said.

Sir James Munby warned that it was not the “proper function” of a judge to rule whether someone would be eligible for such a death, and described the proposals, by Kim Leadbeater, the Labour MP, as “defective”.

In a major intervention in the controversial debate, he suggested it was “not what judges do and not what judges are for”.

Ms Leadbeater published her Private Members’ Bill, the Terminally Ill Adults (End of Life) Bill, on Monday night. The draft legislation gives High Court judges the final decision on whether an assisted death can go ahead.

However, Sir James, one of Britain’s most eminent retired judges, accused the MP of promoting a “profoundly unsatisfactory scheme” that would be open to abuse.

“All in all, in relation to the involvement of the judges in the process, the Leadbeater Bill falls lamentably short of providing adequate safeguards,” he said.