A scientist who recently visited the Great Barrier Reef has said "if it was a person, it would be on life support", as researchers strive to highlight the plight of the reef.

New images have shown the worrying extent of the damage done to the reef by climate change.

Rising water temperatures have damaged the world’s largest reef system, which stretches for over 1,400 miles off the coast of Australia.

In May, researchers found that more than a third of the coral in northern and central parts of the reefs was dead, and 93 per cent of individual reefs had been affected by a condition known as coral bleaching.

This usually leads the corals to die as it ends their symbiotic relationship with algae-like single cell protozoa, which are expelled when corals are exposed to water which is too warm.

Scientists have found that the situation has worsened.

Amanda McKenzie, CEO of the Australian Climate Council, told ABC: "After the bleaching event in May, 60 per cent of what we saw was bleached very white.

"Another 19-20 per cent was covered in sludgy brown algae. Even of what remained healthy, some looked a bit on edge.

"When we went back a few weeks ago to see if they had recovered or died, quite a large proportion had died."

The corals, once brightly coloured, have been bleached white credit: Climate Council

She estimated around half of the bleached corals they visited had died, and that the bleaching had mostly affected delicate corals rather than the stronger 'brain corals'.

However, the researchers discovered that fewer species of fish were found on the reef.

Professor Tim Flannery, who visited the reef in September, toldABC: "We wanted to see how much repair there'd been, but the coral we saw bleached and in danger a few months back has now mostly died.

A diagram showing the difference between stressed, dead and healthy coral credit: Climate Council

"On top of that we've seen a whole lot of new damage, a whole lot of white coral out there that's been killed by Crown of Thorns starfish because it was too weak to defend itself.

"If it [the reef] was a person, it would be on life support".

Tourism operator John Rumney, who has been visiting the reef for 15 years, told the news outlet he had also noticed a decrease in the amount of fish.

"The experience is still fantastic, but tourists don't know what they're looking at. They don't know what it should look like," he said.