Lawyers for a former US fighter pilot are urging the United Nations to investigate the "degrading" treatment he's receiving in an Australian prison, with his wife saying he has become a "shadow" of his former self.

Daniel Duggan, a 54-year-old Australian citizen, was arrested in October by federal police in the New South Wales town of Orange, at the request of American authorities who accuse him of helping train the Chinese military to fly jet fighters.

At the end of last year, the federal government approved a request from Washington to extradite the former pilot, who has renounced his American citizenship, with authorities in the US alleging Mr Duggan had breached money laundering and arms export control laws.

Last week ASIO director-general Mike Burgess confirmed the intelligence agency had detected a small number of former defence personnel choosing "cash over country" to work for authoritarian regimes, describing them as more "top tools" than "top guns".

In a submission to the UN Human Rights Commission sent earlier this month, Mr Duggan's lawyers say his treatment in prison – where he is confined in a two-by-four-metre cell – constitutes four breaches of the International Covenant on Civil and Political Rights.

The breaches include a failure to protect Mr Duggan from "inhumane or degrading" treatment, a failure to segregate him from convicted prisoners, the violation of his right to adequate facilities to prepare his legal defence, and a denial of his right to confidential communication.

The submission cites a clinical psychologist who interviewed and assessed Mr Duggan in Sydney's Silverwater prison and diagnosed him with severe adjustment disorder, anxiety and depression.

"The psychologist described Mr Duggan's conditions as 'extreme' and 'inhumane'. He advised that Mr Duggan was at risk of a major depressive disorder," the submission states.

According to the submission, Mr Duggan also suffers from a "benign prostatic hyperplasia", but was unable to see a doctor until the first week of February, while his numerous requests to a nurse for multivitamins had not been met.

Mr Duggan's wife Saffrine says her husband has become a "shadow of himself" and described her shock at seeing him in prison recently, which she said was "like being in a zoo, and I wouldn't send my worst enemy there".

Saffrine Duggan also accused authorities of "trying to break" her husband by "slamming him in solitary confinement and maximum security, surrounded by convicted terrorists, murderers, paedophiles".

"There is screaming day and night. They want to break the man I love. An innocent man with a large family who loves him dearly," she said.