A campaigner for medically-assisted suicide has harshly criticised euthanasia advocate Philip Nitschke for helping a man he knew was not terminally ill commit suicide.

Doctor Rodney Syme has been fighting for decades to change the law prohibiting what he calls doctor-assisted death.

• Doctor attacked for helping depressed man die

He is worried that Dr Nitschke’s revelations could undermine those efforts.

Last week the ABC revealed Nigel Brayley, 45, of Perth, had sent Dr Nitschke emails in which he stated he was not terminally ill, but was “suffering”.

His friends say Mr Brayley was depressed.

After their correspondence, Dr Nitschke advised Mr Brayley on how he could end his life.

The euthanasia campaigner said he had done nothing wrong.

“If a person comes along to me and says they’ve made a rational decision to end their life in two weeks, I don’t go along and say, oh, have you made a rational decision, do you think you’d better think about it,” Dr Nitschke said.

Dr Syme says that attitude is just one indication Dr Nitschke is far from the mainstream on the issue of assisted suicide.

“He represents a maverick who’s on the extreme end of the debate,” he said.

“What I want people to understand is that this has got nothing to do with the legislative process for creating voluntary-assisted dying.

“I am concerned, and I have argued what he does is in many ways irresponsible.

“Because if somebody is going to consider ending their life they should have expert advice.”

Dr Syme is worried many will confuse his advocacy group, Dying With Dignity, with Dr Nitschke’s Exit International.

He is eager to make sure the public sees that there is “a huge gap” between his advocacy group and the controversial views of Dr Nitschke.

“He is fundamentally not supported by the organisations who support Dying With Dignity,” Dr Syme said.