The Abbott government’s claim that the Great Barrier Reef isn’t in danger defies all available science including its own, a leading world expert on coral reefs says.

Professor Terry Hughes, who is the director of the Australian Research Council Centre of Excellence for Coral Reef Studies, says there’s an extraordinary disconnect between the government’s position and what scientists across the globe are saying.

He said even the federal government’s own reef outlook report, released earlier this year, found the reef was in poor condition and was deteriorating, with climate change the primary threat.

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Foreign Minister Julie Bishop this week challenged US President Barack Obama over his climate change speech on the sidelines of the G20 summit in Brisbane.

She said her office had sent President Obama a briefing on federal preservation efforts, after he used the speech to warn natural wonders like the reef were under direct threat without climate change action.

“We do not believe that it is in danger,” Ms Bishop told Sky News on Friday.

“In fact the Australian government is making every effort to ensure that the Great Barrier Reef is preserved for generations to come.”

The briefing cited a ban on resource exploration and dredge dumping near the reef and the $180 million annually provided by the federal and state governments to manage the reef’s health.

Prof Hughes said he couldn’t explain why Ms Bishop’s views were so far removed from the science.

“I think you’ll have to ask her that,” he told AAP.

“It’s just not credible to say you are protecting the Great Barrier Reef while doing nothing about climate change.”

He said scientists had also roundly condemned the federal government’s recent draft 2050 reef plan.

“The focus of the plan isn’t protection and conservation … rather it’s about sustainable development,” he said.

Deputy opposition leader Tanya Plibersek accused Ms Bishop of insulting the US president.

“She’s berating the president of the United States,” Ms Plibersek said in Sydney.

“This is an extraordinarily petulant performance.”

Government support for the development of the vast Carmichael coal mine in the Galilee basin is also inconsistent with reef protection, he said.

“(The mine) will have a Co2 footprint that’s three times larger than New Zealand’s if it goes ahead,” he said.

“I loved Obama’s speech. I thought it was spot on. And it really highlights how out of step Australia’s climate change policy is.”

Professor Ove Hoegh-Guldberg, head of University of Queensland’s Global Change Institute, applauded Mr Obama’s speech, adding that coral cover had shrunk by half over the past three decades.  

He said climate change was one of the major threats to the reef as it increased the ocean’s acidity.

“It’s just chemistry … you can’t deny that,” he told Fairfax.

“We have one of the jewels of the planet in our possession and we should care a lot about climate and he (Mr Obama) wasn’t getting that from our leader.”

UNESCO has given Australia until February to show it is properly managing the reef. If it’s not satisfied with the response, the reef could be listed as a World Heritage site in danger.