Doctors in Perth are threatening to stop Australia's oldest scientist flying to Switzerland to end his life through voluntary euthanasia.

Edith Cowan University honorary research associate David Goodall doesn't have a terminal illness but his quality of life has deteriorated at age 104.

Euthanasia campaigner Philip Nitschke said Professor Goodall attempted suicide about two months ago after suffering a fall, ended up in hospital and his daughter had to fight hard to get him out - only succeeding after arranging an independent psychiatric review.

"The doctors started to say 'he's talking about ending his life, there's nothing much wrong with him, so therefore he's a risk to himself'," Dr Nitschke told AAP.

He said Prof Goodall was keen to leave the country after the hospital experience.

"On the basis of that, he said 'enough is enough - now's the time to die'," Dr Nitschke said.

And now the doctors who treated him are threatening to prevent him from leaving the country, arguing he's a danger to himself and not fit to travel, which "the airline would respond to", Dr Nitschke said.

"I don't know whether they would be successful or whether it's just a threat.

"It's worrying the hell out of David and his daughter."

Dr Nitschke urged the doctors to "back off".

Marshall Perron, the former Northern Territory chief minister who introduced Australia's first voluntary euthanasia legislation, said it was tragic Prof Goodall couldn't have his wishes met at home.

"I understand his plight and fully support what he's trying to do," Mr Perron told AAP.

"Philip is very keen to push for those people who are not terminally ill to have access to die - the rest of us are a bit more cautious than that.

"However ... the average person who gets to be 100-plus ought to be able to have the right to say when they believe they've lived their life to the full and would rather not continue."

Mr Perron said he gave credit to WA Premier Mark McGowan for wanting to introduce assisted dying legislation but his plans didn't go far enough.

While Mr McGowan says he feels deeply for Prof Goodall, he only supports voluntary euthanasia for terminally ill people.

"It's all very well for politicians to say 'I have sympathy' but they are actually in a position to be able to do things," Mr Perron said.

"The time to act is while you have the reins of government.

"Let's hope that he does the right thing at the end of the day."

A WA parliamentary inquiry into end-of-life choices is due to submit its recommendations to parliament in August.

Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.

Suicide Call Back Service 1300 659 467.