Mr Morrison also denied a Fairfax Media report that Customs would make further inquiries into claims asylum seekers had their hands held against hot pipes.

He said ''a hysterical chorus'' calling for an inquiry into the matter would only ''legitimise these false claims''.

''To consider this matter further without any substantiation to the claims put forward, other than repetition, would simply give credibility to something that has none,'' he said.

The Australian Customs and Border Protection Service issued a statement on Saturday saying no new inquiry or investigation was under way and that the abuse claims were ''assessed at the time they were first made and found to be without foundation''.

''No new evidence has been presented which would warrant further action at this time.''

Fairfax Media stands by its report that Customs will review the information that form the basis of the denials.

After Fairfax published detailed allegations on Thursday from a Sudanese man who says he witnessed sailors forcing the hands of three asylum seekers onto a hot engine pipe, the government and Defence again refused to say why they were so certain the allegations were untrue.

The government has consistently refused to detail the basis of its categorical denials, saying only that operational debriefs were routinely conducted ''as part of normal Border Protection Command procedure''.

The government has previously said Australian authorities have not spoken with the asylum seekers at the heart of the claims.

Fairfax believes a standard ''quick assessment'' was carried out, similar to initial inquiries conducted when Australian Defence Force personnel are involved in incidents while fighting overseas.

This is likely to have involved informal interviews with members of the navy boarding party that undertook the asylum-seeker boat turn-back about January 6.

On Saturday, Labor backbencher Matt Thistlethwaite told Sky News that to settle the issue once and for all, the claims should be independently investigated.

''We should be bringing a healthy scepticism to these claims but now they've been aired again by Fairfax, the appropriate course is to have them independently investigated,'' he said.

''That's the best way to vindicate the Australian Navy [and] I have every confidence in Australian Navy personnel.''

Mr Morrison said Mr Thistlethwaite's call for an independent inquiry was ''a vote of no confidence by Labor in the Australians who serve our country by protecting our borders''.

''Unlike the Labor Party, the government will continue to back our navy and customs personnel in the face of these wild, unsubstantiated allegations,'' Mr Morrison said.

''The fact that media continue to recycle the same wild and unsubstantiated claims does not make them any more true or any more worthy of further inquiry than when they were first reported and rejected. Nothing has changed.''