More than half a million hectares of forest was cleared in the Great Barrier Reef catchments over four years – an area more than twice the size of the Australian Capital Territory.
Official environment and energy department data shows that 596,000 hectares of forest was cleared between 1 July 2012 and 30 June 2016.
Labor’s environment spokesman, Tony Burke, said “land clearing of this scale should never have been permitted”.
“It’s a destruction of habitat and a disaster for the Great Barrier Reef,” Burke said.
“The Liberal party seems to think that they can turn a blind eye to the destruction of the environment and runoff into the Great Barrier Reef and then throw money to private organisations and pretend that the vandalism never occurred.”
Conservationists described the figure as “diabolical” and said it demonstrated the Turnbull government had failed to rein in deforestation at a time when it is trying to improve the health of the Great Barrier Reef.
“Over half a million hectares of forests bulldozed in reef catchments since 2012 constitutes an environmental crisis,” said Jess Panegyres, the national nature campaigner at the Wilderness Society.
“This revelation is a moment of reckoning for the Turnbull government. If they care at all about Great Barrier Reef water quality, they must rein in the bulldozers starting today.”
Deforestation accelerates sediment and nutrient runoff into the reef, which stimulates algae growth and can smother corals.
After climate change, poor water quality is the biggest threat to the Great Barrier Reef and billions of dollars has been spent to try to manage the problem.
But environment groups and the Greens say the situation won’t improve until governments address the issue of land clearing and strengthen national environment laws, which they say have become too focused on facilitating development rather than protecting the environment.
The Greens’ environment and biodiversity spokesman, Andrew Bartlett, said “we need to do a lot better with regards to controlling land clearing”.
“Those figures are staggering and it shows both the need to strengthen the existing laws federally and better enforce what’s already there,” he said.
“We’re already on record wanting strong improvements in this area, but these figures show it’s all the more urgent.”
In March the government pledged $500m for the reef, including $201m that would be spent on water quality measures such as improving land management practices.
But it has come under scrutiny for announcing that $444m of that funding will go to the Great Barrier Reef Foundation, a not-for-profit group with six full-time staff.
The environment minister, Josh Frydenberg, is overseas. Guardian Australia asked the assistant environment minister, Melissa Price, how the high levels of land clearing fit with the government’s plan to improve the reef’s health but has not received a response.
An environment and energy department spokesperson said the 596,000-hectare figure represented human-caused clearing of forest land for conversion to other land uses such as grazing or cropping.
The figure does not include clearing of land not classified as forest, such as sub-forest woody vegetation.