A leading mental health expert and a long-serving member of the Government's advisory council on detention and asylum seekers has quit after more than 10 years in the job.

Professor Harry Minas, a mental health expert from the University of Melbourne, says he is frustrated with policy on the issue and that he can no longer make a meaningful contribution.

He says the decision by the Government to excise the mainland from the migration zone and deny those who arrive by boat the right to work cemented his decision.

"For people who are already vulnerable I think is really too much to think about," he said.

"I think that represents a really major disregard for our obligation to asylum seekers and refugees."

Professor Minas had been a member of the council since 2001. He says he had thought about quitting the council earlier.

He says the quality of political leadership around the issue has been "appalling".

"I don't know how you change it. If I knew that I think we might have had a better quality discussion and debate about these issues," he said.

"We've through periods over the past decade and more where asylum seekers have been vilified by various people in the community and also by some politicians, where all sorts of outrageous claims have been made about what's going to happen because we've lost control of our borders and so on.

"I don't think any of that is helpful."

But Professor Minas says Immigration Minister Chris Bowen is doing the "very best he can" in the circumstances.

"I don't doubt his intentions or his capability. I think we have a political environment at the moment which makes it very difficult to do the right thing," he said.

"I don't know how much influence I've ever had but, you know, I think there are points at which decisions are made that I just can't support.

Professor Minas wrote a letter of resignation to Mr Bowen, but has had no response from his office.