The search for the missing Malaysia Airlines flight MH370 may be scaled back, Australia’s Prime Minister has said, while also expressing hope the plane could still be found a year after it vanished.

The plane disappeared en route from Kuala Lumpur to Beijing on March 8, 2014 with 239 people on board. No trace has been found despite a massive surface and underwater hunt.

"I can't promise that the search will go on at this intensity forever but we will continue our very best efforts to resolve this mystery and provide some answers," Tony Abbott told parliament on Thursday in the capital Canberra.

"I do reassure the families of our hope and expectation that the ongoing search will succeed."

Australia is leading the hunt in the Indian Ocean, about 1,600km off its west coast, with four ships using sophisticated sonar systems to scour a huge underwater area.

The vessels are focusing on a 60,000 square kilometre priority zone, with the hunt scheduled to end in May.

More than 26,000 square kilometres, or 40 percent, of the ocean floor has been explored to date.

The intensive search - jointly funded by Australia and Malaysia with a budget of $93m - has so far only turned up a few shipping containers.

The ships, Fugro Supporter, Fugro Equator, Fugro Discovery and GO Phoenix, are working in one of the world's most isolated locations in treacherous conditions similar to the "Roaring Forties" north of Antarctica - notorious among mariners for its hostile seas.

Weather conditions in the remote region are expected to worsen after May.

'In our thoughts'

The agency coordinating the search, the Australian Transport Safety Bureau, has previously said a decision on continuing after the current hunt was completed was up to the Australian and Malaysian governments.

The families of some of the Australian victims - Rodney and Mary Burrows, Catherine and Robert Lawton, and Paul Weeks - were in parliament when Abbott made his statement.

They were joined by the Malaysian High Commissioner Zainal Abidin Ahmad, Chinese ambassador Ma Zhaoxu and representatives of other nations that lost citizens on the flight. 

"The message of this parliament to all of the families of MH370 is that you remain in our thoughts and prayers," the Australian prime minister said.

"To you - and to all those with loved ones aboard that flight - my pledge is that we are taking every reasonable step to bring your uncertainty to an end."

Many relatives were incensed when on January 29 Malaysia declared that all on board were presumed dead and that families should seek compensation.

Source: AFP