The Turnbull government has refused to release documents about the construction of new asylum seeker facilities on Manus Island, saying doing so would damage Australia's relationship with Papua New Guinea.

But the Australian Greens think the real reason has more to do with Immigration Minister Peter Dutton not wanting to be politically embarrassed.

Greens immigration spokesman Nick McKim and fellow crossbencher Stirling Griff convinced the upper house in December to demand documents about construction of the West Lorengau Haus accommodation, fencing and essential services.

Asylum seekers and refugees were forcibly moved to West Lorengau and two other new facilities after the Manus immigration processing centre was closed at the end of October.

But at the time there were repeated reports, including from the United Nations' refugee agency, the new accommodation was unfinished and insufficient to host all the men.

Mr Dutton insisted they were completed and had full services.

In a letter to the Senate president tabled this week, the minister warned releasing information about the West Lorengau construction and provision of services would damage Australia's international relations.

"The confidence of the two countries presently partnering with Australia in arrangements for regional processing is critical to the continuing success of Operation Sovereign Borders," Mr Dutton said.

"Unilateral disclosure by Australia ... would undermine PNG's confidence in its good working relationship with Australia and might reasonably be expected to jeopardize (sic) co-operation on people smuggling matters."

Senator McKim says this reasoning is "completely spurious" and appears designed to avoid political embarrassment.

"The reason Peter Dutton does not want to release these documents is because doing so would expose him as the liar that he is," he told AAP from Manus Island, on his fifth trip to inspect at conditions for refugees and asylum seekers.

"I've spoken to a large number of refugees over the last couple of days and there are still contractors working on one of the facilities now.

"I'm 100 per cent certain that Peter Dutton lied through his teeth when he claimed that these facilities were ready in early November last year."