Archbishop of Melbourne Peter Comensoli. Credit:Eddie Jim

As Victoria rolls out its historic legalised assisted dying scheme, Catholic bishops have issued an eleventh-hour warning against doctors using the contentious laws to help patients end their lives.

The laws come into force on Wednesday and allow terminally ill adults who have only about six months to live and meet other strict eligibility criteria – such as being able to give informed consent – access to a lethal substance.

A letter signed by four Victorian bishops, including Archbishop of Melbourne, Peter Comensoli, warns the new laws will mark "a new, and deeply troubling chapter of health care".

"We cannot co-operate with the facilitation of suicide, even when it seems motivated by empathy or kindness," the letter signed by the bishops of Melbourne, Ballarat, Sale and Sandhurst said.