A UN delegation has again recommended the Great Barrier Reef be added to the World Heritage 'in danger' list, and urged "ambitious, rapid and sustained" action on climate change to protect the site.

The UNESCO report comes after an official visit to monitor the reef in March, and recommends the Commonwealth and Queensland governments both adopt stronger emissions reductions policies consistent with stopping warming at 1.5C.

It cites frequent mass bleachings and increased water acidity among the increased threats to corals, impacts which can be attributed to uncurbed emissions.

UNESCO has advised greater investment in water quality, recommendations which will see mounting pressure on the Albanese government.

Although Labor has strengthened Australia's climate policies and invested more in the Great Barrier Reef, its policies and actions are not in line with the recommendations made by the UNESCO report.