The Catholic Church has mobilised a grassroots campaign against voluntary assisted dying laws in NSW, with parishioners, school staff and parents urged to petition politicians weeks before a bill goes before state parliament.

Bishop Peter Comensoli, the designated spokesman for Catholic bishops on the voluntary euthanasia issue, has organised distribution of the petition to 26 parishes and more than 40 schools in his diocese of Broken Bay, covering Sydney's north shore, northern beaches and the Central Coast.

The petition has also been sent by Bishop Comensoli to the 10 other Catholic dioceses across NSW, "strongly encouraging" them to do the same.

Bishop Comensoli told Fairfax Media he was "encouraging our people to get behind this and have their voice heard".