United States-based Earthjustice International says the current level of coral bleaching on the Great Barrier Reef amounts to a world heritage crisis.
Latest assessments also show the overall condition of the reef remains poor.
Earthjustice lawyer Noni Austin says the situation requires urgent attention from the World Heritage Committee.
Last year, the World Heritage Committee decided against putting the Great Barrier Reef on its in-danger list.
It recommended Australia monitor the area and provide an update on its 2050 reef plan.
But pressure is now mounting to address deadly changes to the reef.
World Wildlife Fund's Richard Leck says the reef is in trouble.
He says the latest poor health assessment didn't even include a recent mass bleaching event.
This bleaching event, caused by warmer water temperatures, has damaged or killed many corals, with scientists reporting significant mortality rates.
Earthjustice International says Australia must immediately act to protect the reef from the effects of climate change.
However One Nation Senator Malcolm Roberts is rejecting claims that climate change is behind reef degradation.
He says the climate change claim isn't substantiated by any empirical evidence, and the reef is fine.
Earthjustice is calling for Australia not to approve or support development ventures that will harm the reef.
Noni Austin says the World Heritage Committee should urge Australia to reject coal projects.
But the Senator also has objections more broadly to the World Heritage Committee's interest in the Great Barrier Reef.
He says it's none of their business.
The World Wildlife Fund's Richard Leck strenuously disagrees.
