Schapelle Corby has gone insane and will not survive her 20-year sentence unless she is moved out of Bali's Kerobokan jail, a top Australian psychiatrist has warned.

Associate Professor Jonathan Phillips, who is believed to have been employed by the Corby family, visited Corby in prison earlier this month and says the former beauty student is "hanging on by a thread".

"She is lost in her own bewildering world where fantasy, hallucinations and bizarre ideas dominate her mind," Dr Phillips told New Idea magazine.

Tormented ... Schapelle Corby last year. Photo: AFP

Dr Phillips, former president of the Royal Australian and New Zealand College of Psychiatrists, says the 32-year-old will continue to deteriorate unless she is moved.

"Even if Schapelle got really good medical treatment in jail the place itself would destroy her, given her now precarious condition," he said.

"I really fear for her.

"I know from experience that her illness will not get any better in the current situation, and will probably worsen with the risk of calamity.

"Whether she's innocent or guilty, her needs are medical."

Dr Phillips says the best option would be to have Corby transferred as a prisoner to Australia and treated in a secure hospital setting.

Failing that, she should go to a psychiatric facility in Bali, he said.

Dr Phillips says he is certain Corby's condition is genuine.

"Let me make it clear, I have been a psychiatrist for many years and I approach my work with proper clinical scepticism.

"She is not putting this on.

"She is in the deepest of pain and her personal world is coming apart.

"Her mind is now playing dreadful tricks on her.

"She can get no peace because she is sure she is being filmed at all times for bizarre purposes.

"She sees highly personalised and critical messages in books, on television and in videos, and she is sure that others are conspiring to end her life.

"She is in huge trouble."

Dr Phillips said he was appalled that other prisoners took responsibility for giving Corby her medication.

"I've never known a similar situation before and the things that might go wrong are beyond reckoning."

The Corby family will send Dr Phillips' 20-page report to Prime Minister Kevin Rudd and other political leaders in the hope it may pressure them to press for Corby's transfer.

Sister Mercedes said she was not surprised by the report.

"It's really, really sad to see it all written down in black and white," she told the magazine.

"It makes me feel helpless.

"We have to get her out of prison to a place where she can be properly looked after."

Corby's sister Mercedes has told a local news outlet in Bali a psychiatrist had been treating the 32-year-old since she tried to scale a water tower inside Kerokoban jail earlier this month.

News and travelwebsite Balebali.com said prison authorities had to coax Corby down to safety recently.

In June, she spent several days in an Indonesian hospital for treatment for depression after she reportedly claimed people were trying to spy on her through holes in the ceiling of her prison cell.

"We are trying to get her better. Every day is difficult and she is not good," Mercedes Corby told the website.

Last week, Corby had four months shaved off her 20-year jail term as part of Indonesia's Independence Day celebrations.

Corby, 32, was sentenced to 20 years' jail after she was caught at Bali's airport in October 2004 with 4.1 kilograms of marijuana in her boogie board bag.

She was last week given a four-month sentence cut as part of Indonesian Independence Day celebrations.