The immigration department's chief medical officer believes the practice of using a Port Moresby motel as a makeshift hospital for sick asylum seekers is flawed.

Documents obtained by AAP under Freedom of Information show the department has been renting rooms at the Granville Motel since May 2014.

The rooms have accommodated asylum seekers and interpreters transferred from the Manus Island detention centre to the Papua New Guinea capital for medical appointments.

The department has kept the accommodation costs secret.

However, one document suggests the overall cost of renting nine twin rooms and four single rooms for 10 fortnights across a four-month period last year was more than the procurement threshold of $80,000.

The motel has 134 rooms, air-conditioning, satellite TV, a swimming pool, restaurant, poolside bar, tennis court, poker machines and chauffeur-driven stretch limousine hire, according to online tourism information.

A log of incidents involving asylum seekers at the motel reveals:

* There was an electrical fire at the motel in May 2015. Asylum seekers were left without power but were not required to evacuate.

* An asylum seeker with a suspected case of tuberculosis stayed at the motel under guard rather than a hospital in April 2015. When test results proved positive he was kept isolated in his room while staff were given masks and gloves.

* Transfield security used "unplanned force" on asylum seekers displaying abusive and aggressive behaviour during incidents in May 2015 and December 2014.

* An asylum seeker threw a motel refrigerator on the floor in January 2015.

In a heavily blacked-out report, chief medical officer Paul Douglas criticised the practice of sending asylum seekers to Port Moresby for specialist appointments.

There was a full-time Australian nurse assisted by a locally trained nurse who provided supervision at the motel, he noted.

"The current process seems flawed and could be better supported by providing more services on-site at Manus," Dr Douglas wrote.

The International Health and Medical Services clinic at the detention centre had an open-ended referral process.

This led to a large degree of over-servicing from the specialists who were ordering investigations that may not change care, as well as excessive delays where one test led to another, he said.

Dr Douglas said some asylum seekers were refusing medical treatment when they arrive in Port Moresby but once they return to the detention centre, doctors referred them back again.