Authorities undertaking the search for the Malaysia Airlines Flight MH370 have come under fire from relatives of the passengers on board the Boeing 777, after they refused to release material pertaining to the missing aircraft.

The Australian newspaper, which tried to obtain information via a Freedom of Information (FOI) request, said that the Australian Transport Safety Bureau's Chief Commissioner Greg Hood invoked the Transport Safety Investigation Act in rejecting the request.

He said the act covers the FOI request for critical documents the ATSB claims support its "ghost flight" and "death dive" scenario, which officials claim resulted in the Boeing 777 going down in an unpiloted crash.

The newspaper was trying to get access to the opinions of international experts, including those from the US and British air crash agencies, Boeing, aerospace group Thales and the British satellite group Inmarsat.

The Australian claims that some ATSB officials are having "second thoughts" about the agency's official line that the pilots on board were either unconscious or dead at the end of the flight.

In February, ATSB general manager for strategic capability, Colin McNamara threw out The Australian's FOI request, claiming the information could "cause damage to the international relations of the commonwealth."

Following an internal review of McNamara's decision, Hood also refused to release the documents sought, saying: "The activities of the ATSB with respect in assisting the Malaysian investigation are covered by the TSI Act."

He also warned that if a serving or former ATSB staff or consultant "discloses information to any person or to a court; and the information is restricted," they have breached the act. Any breach carries a two year jail sentence, The Australian reported.

Malaysia says not hiding anything

Kuala Lumpur, Malaysia
The fate of MH370 is one of aviation's biggest unsolved mysteriesReuters

Meanwhile Malaysian Transport Minister Liow Tiong Lai said that it was unfair to accuse the Malaysian and Australian governments of hiding information.

He said that all next-of-kin of those on board the missing flight have been given access to the latest details on the investigation, which is published on a website and updated weekly.

"Wait for a full investigation report to come out, then everyone will get to see it. We cannot give everybody these details," he said, reports FreeMalaysiaToday.com.

He told the website that Malaysia was "very thankful to Australia and China, who have helped us all along."

Malaysia Airlines
Malaysia's transport minister Liow Tiong Lai at a news conference about debris found on a beach in Mozambique.Reuters

The final report on the investigation into the missing aircraft is expected to be released at the end of the year. He said that the seven-member International Civil Aviation Annexe 13 safety investigation team led by Kok Soo Chon, the former Malaysian Civil Aviation Department director-general, was working "around the clock to complete the investigation."

The investigation team comprises aviation experts from the US, China, France, Australia as well as from Boeing and Inmarsat.

MH370, with a total of 239 passengers and staff on board was flying from Kuala Lumpur to Beijing on 8 March, 2014 when it disappeared.

Satellite tracking data appears to confirm that the plane crashed in the Indian Ocean, southwest of Australia, but a massive underwater search operation led by the ATSB and funded by Australia, China and Malaysia was called off in January 2017 after failing to locate the aircraft.