The International Union for Conservation of Nature has recommended against removing vast swathes of Tasmanian forest from world heritage protection, in an embarrassing setback for the Australian government.

The IUCN, the world’s largest conservation organisation, said overnight in Paris there was no ecological justification for the removal of 74,000 hectares of Tasmanian forest from the world heritage zone.

The IUCN's report said the proposed removal was "clearly inappropriate for consideration as a minor boundary modification". It would "impact negatively on the outstanding universal value of the property" and "reduce integrity of key natural attributes".

It criticised the government's proposal for providing "relatively scant information" to support its case and said the way the boundaries had been drawn for the proposed excision appeared "somewhat arbitrary".

"The proposals also appear to reinstate threats that have previously been noted as being of concern by the World Heritage Committee, such as increasing the potential for adjoining logging to impact the property, or create additional risks in relation to fire management," the report said.

The recommendation is a humiliating outcome for the Coalition government, which pledged to redraw Tasmania’s world heritage map, just a year after the previous Labor government got world heritage approval for an extension of the protected area.

Unesco’s World Heritage Committee still has to make a final decision on the government’s request for a boundary change, but the IUCN’s recommendation will heavily influence the outcome. A separate recommendation will be made on the cultural, rather than natural, significance of Tasmania’s protected forests.

The Coalition applied to remove 74,000ha from the world heritage area, claiming Labor’s nomination of 170,000ha was rushed, failed to consult local communities and was damaging for Tasmania’s economy.

The government argues there are more than 100 “degraded” areas from previous logging within the protected zone, meaning it should be opened up again to the forestry industry.

However, a Senate inquiry published last week concluded that less than 5% of the 74,000ha had ever been disturbed, and degraded areas did not justifying the delisting in any case. The committee, which split down party lines, said the application was “fundamentally flawed” and would damage Australia’s international reputation.

The IUCN report found that about 85% of the area proposed for excision was natural forest, and 45% was old-growth forest. Only 10% of the area had been regenerating from logging since 1960, and only about 4% of the area could be regarded as having been heavily disturbed, it found.

The Greens leader, Christine Milne, welcomed the recommendation as “the best possible result – for Tasmania’s forests, Australia’s international reputation and the integrity of world heritage sites everywhere".

She called on Tony Abbott to withdraw the application to adjust the boundary, calling it a "demeaning act of environmental vandalism".

“The expert bodies that advise the World Heritage Committee have condemned the Australian government for failing to provide any evidence of their claim that large parts of the forest are degraded," Milne said.



The environment minister's office has been contacted for comment.

The World Heritage Committee has previously changed the boundaries of protected sites, but it has stated its surprise at the Coalition’s stance on Tasmania’s forests given the short time since its inscription.

Environmentalists are vehemently opposed to the delisting, while the forestry industry has expressed reticence over the idea due to fears there will be no buyers for such controversially obtained timber.

The extension of the world heritage area was part of the forestry peace process in Tasmania, which pitted loggers against environmentalists over several decades.

This week Guardian Australia revealed that the Australian Environment Foundation, a group set up by the libertarian thinktank the Institute of Public Affairs, lobbied the 21 nations on the World Heritage Committee to allow the government to alter the boundary.