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".

"I'm providing the information to assist the people of the diocese informing their conscience about euthanasia," he said.

Bishop Comensoli said the petition was supplied to him by Labor MLC Greg Donnelly, a well-known opponent of voluntary euthanasia laws.

Ms Donnelly said she has been "sending petitions to many, many people around the state. He might have ended up with a copy".

A brochure accompanying the petition sent by Bishop Comensoli states: "The true mark of our humanity is witnessed in the steadfast care we give to those we love as they are dying."

It warns that if the NSW bill becomes law "it would radically abandon our deep human commitment not to deliberately take someone's life".

The brochure is produced by the HOPE organisation, a collection of groups opposed to voluntary assisted dying laws.

Nationals MLC Trevor Khan, a member of the cross-party working group on the voluntary assisted dying bill, criticised the decision to send the material to schools.

"The churches are entirely entitled to motivate their parishioners from the pulpit," he said.

"The question is whether they should actually be doing it through the playground in schools.

"You don't use the mechanism of a school for the purposes of simply talking to principals and teachers. The only mechanism to get it home is through the children."

However Bishop Comensoli said the material was not being sent to children and rejected Mr Khan's criticism as "a disingenuous statement".

"It has gone to parents and the way we do it in our diocese is in emails directly to parents," he said.

Dying with Dignity, which is supporting the bill, has arranged for Dr Leigh Dolin, who was president of the Oregon Medical Association during the debate that led to legalised assisted dying there in 1996-97, to speak to NSW MPs.

The voluntary assisted dying bill is due to be debated in the NSW upper house in mid-September. It would allow terminally ill NSW residents aged at least 25 to end their own lives with medical assistance.

A patient must be likely to die of their illness within 12 months, the decision signed off by two medical practitioners and the patient assessed by an independent psychiatrist or psychologist.