US-based Earthjustice and Environmental Justice Australia on Thursday unveiled legal analysis in Paris that they said demonstrates Australia was failing to fulfil responsibilities to protect and conserve the reef.

They also called on the World Heritage Committee to finally give priority to climate change following widespread coral bleaching in 2016 that resulted in the death of about one-fifth of the Great Barrier Reef's corals alone.

The demand comes as the US National Oceanic and Atmospheric Administration's Coral Reef Watch pointed to many reefs facing the threat of renewed bleaching in 2017, including the Great Barrier Reef. (See chart above)

"Over the past three years, almost all of the world's reefs have experienced summertime heat stress, with more than 40 per cent of reef locations accumulating stress to a level where we expect coral bleaching", said Dr Scott Heron of NOAA's Coral Reef Watch from Townsville.

"At present, many southern hemisphere reefs are at or near bleaching levels, including in the Great Barrier Reef and the South Pacific - and some of those for the second time in the three-year period."

'More dire'

"Corals around the world are bleaching and dying because of ocean warming and acidification caused by out-of-control greenhouse gas emissions," Noni Austin, an Earthjustice lawyer and report author, said. "The plight of these corals - and of the World Heritage sites on which they depend - is growing more dire every year."

"It's ambitious and it sets out in law and science, what [nations] could and should do," said Ariane Wilkinson, lawyer at not-for-profit law firm Environmental Justice Australia, another of the authors.

"It's very clear that by mid-century, many coral places will not survive," Ms Wilkinson said, adding that the necessary action had to include halts to major new fossil-fuel projects such as those planned in Queensland.

The report's release comes as lobbying of the World Heritage Committee's 21 members intensifies ahead of a meeting in Krakow, Poland, in July. The groups want the committee to finally give priority to climate change.

"The committee can't squirm out of it any more.They've got to focus on it," said Jon Day, formerly a director of the Great Barrier Reef Marine Park Authority and an ex-Australian government official who attended 11 committee meetings between 1998 and 2013. "It isn't just about the [Great Barrier] reef - it's affecting many, many of their world heritage sites."

Dr Day said he had recently been in France showing World Heritage delegates photographs of the reef's bleaching. "Committee members were pretty shocked to see what corals looked like after bleaching," he said.

'In-danger watch list'

The Abbott government managed to have the Great Barrier Reef removed from the in-danger watch list, prior to last year's big bleaching event and further bleaching in 2017.

Dr Day said that the committee may consider putting the reef back on the watch list. While such a move would place the reef back in the global spotlight - and the government's policies - it would not remove the threat.

"The thing that's going to fix the problem is when the government and the world start to address climate change ... which is what the papers [such as the legal groups] are trying to do," he said.

Josh Frydenberg, the environment and energy minister, said the federal and Queensland governments would spend $2 billion over the next decade to support the reef's health, including to improve water quality, remove the crown of thorns starfish and bolster scientific knowledge.

"In the first 18 months of the 35-year [Reef 2050] Plan significant progress has been made including a ban on the disposal of dredge material in the World Heritage Area," he said, adding that "global efforts to tackle climate change are critical to the long-term outlook for coral reefs around the world, including the Great Barrier Reef".