A crown-of-thorns starfish feeding on coral on Australia's Great Barrier Reef.

The reef is in poor condition and the state of inshore areas along its 2,300km length is not improving quickly enough, a report released this week warned.

The study by the Queensland state government found that the reef has lost half its coral cover over the past 30 years. Scientists at the Australian Institute of Marine Science warned in 2011 that the crown-of-thorns starfish was responsible for about 40 per cent of coral loss since the 1980s.

However, researchers at Queensland's James Cook University have revealed that household vinegar can help kill outbreaks of the venomous starfish. A recent trial involved injecting the starfish with 20ml of vinegar, resulting in a 100 per cent kill rate within 48 hours of injection.