The conservative government, already under fire from environmentalists for joining the United States in rejecting the Kyoto pact on cutting greenhouse gas emissions, declined to comment.

But environmental groups and opposition parties pounced on the report to denounce what they saw as government inaction.

"The message on landclearing has been delivered to the government time and time again, in any number of similar reports in recent years," said Nicola Beynon, spokeswoman for the Australian branch of Humane Society International.

"The national Biodiversity Audit has to be the final call to action."

The main opposition party, centre-left Labour, said 500,000 hectares (1.236 million acres) of the vast island continent, home to some of the least populated areas in the world, was lost to landclearing every year.

"Unless urgent action is taken now, much of Australia's unique wildlife faces the threat of extinction," Labor's environment spokesman, Kelvin Thomson, said.

Long isolated from the rest of the world, Australia retains a unique biodiversity and unique animal species, such as the kangaroo.

But it has lost dozens of native species following the introduction of European animals, crops and pests after Britain established its first penal colony here in 1788.

"Past generations may have sleepwalked through extinctions like that of the Tasmanian tiger. We are about to do it with our eyes open," John Connor, campaign director of the Australian Conservation Foundation, told the Australian Associated Press news agency.