An Australian academic held in a Tehran prison has said she rejected an offer from Iran to become a spy in exchange for her release.

Key points: Dr Moore-Gilbert said in a letter that her health "has deteriorated significantly"

Dr Moore-Gilbert said in a letter that her health "has deteriorated significantly" She said she would not change her decision on the offer to spy for Iran under any circumstances

She said she would not change her decision on the offer to spy for Iran under any circumstances Dr Moore-Gilbert said it was "inhumane" being denied opportunities to speak to her family

Melbourne University lecturer Kylie Moore-Gilbert has been held in the notorious Evin prison in Tehran since October 2018, serving 10 years for espionage.

In extracts of multiple handwritten letters smuggled out of prison — published by The Guardian and Times of London — Dr Gilbert-Moore said she had never been a spy and feared for her mental health.

"I am not a spy. I have never been a spy and I have no interest to work for a spying organisation in any country. When I leave Iran, I want to be a free woman and live a free life, not under the shadow of extortion and threats," one of the letters said.

Dr Moore-Gilbert also wrote to her "case manager" in the letter, "please accept this letter as an official and definitive rejection of your offer to me to work with the intelligence branch of the Iranian Revolutionary Guard Corps", the Guardian reported.

"Under no circumstances will I be persuaded to change my decision."

She said she had been denied phone calls to her family and she was repeatedly transferred to hospital due to her failing mental and physical health.

In another letter seen by the Guardian, Dr Moore-Gilbert said her "health has deteriorated significantly" and that it was "really inhumane" not being allowed to speak to her family.

"I think I am in the midst of a serious psychological problem, I can no longer stand the pressures of living in this extremely restrictive detention ward anymore."

A guard inside Tehran's Evin prison where Dr Moore-Gilbert is jailed. ( Reuters: Morteza Nikoubazl )

Evin prison has a reputation for brutal treatment of inmates, including mock executions, beatings and psychological "torture".

Dr Moore-Gilbert is a Middle East expert at the University of Melbourne's Asia Institute, specialising in the Arab Gulf states. She has also studied at Cambridge.

The Federal Government has previously described Dr Moore-Gilbert's situation as complex, and Foreign Minister Marise Payne has said Australia does not accept the spying charges against her.

A recent appeal against her 10-year sentence has failed.

Ms Payne said last Friday that she had raised Dr Moore-Gilbert's fate with her Iranian counterpart Mohammad Javad Zarif, but declined to detail her conversation.

Dr Moore-Gilbert previously has gone on hunger strikes and urged the Australian Government to do more to free her.

'I beg you to act faster'

The Center for Human Rights in Iran has released letters last Friday to the Associated Press (AP) that Dr Moore-Gilbert wrote to Prime Minister Scott Morrison.

In the letters Dr Moore-Gilbert said she had been imprisoned "to extort' her and the Australian Government.

She wrote in June: "I beg you to act faster to bring this terrible trauma that myself and my family must live through day after day to a resolution."

Dr Moore-Gilbert is a Middle East expert at the University of Melbourne's Asia Institute. ( University of Melbourne )

She wrote again in December: "Six months have passed … during this time I have remained in the same prison without any improvement in my intolerable conditions."

"Over the past nine months I have been completely banned from any contact with my family, with the exception of a three-minute phone call [with my father], which was only granted after I took desperate measures which put my own life at risk," she wrote.

"I have undertaken five hunger strikes as my only means to raise my voice, but to no avail. As predicted, I have now received a conviction of 10 years in prison, and my appeal … has failed," she wrote.

"I beg of you, Prime Minister Morrison, to take immediate action, as my physical and mental health continues to deteriorate with every additional day that I remain imprisoned in these conditions," she added.

Ms Moore-Gilbert said she had been "subjected to grievous violations of my legal and human rights, including psychological torture and spending prolonged periods of time in solitary confinement".

"I am writing to you to beseech your government to do more, to make difficult diplomatic decisions if necessary," she said.

ABC/AP