Australia has been accused of bungling international whaling talks and setting back a campaign to save whales.

Conservation groups say Australian officials derailed a motion that would have seen Japan admit that one of the justifications it gave for whaling was dubious.

Japan and other whaling nations say that by culling whales, they are helping preserve dwindling fish stocks.

In talks at the World Conservation Congress held this month in Spain, Japan and other whaling nations were reportedly ready to sign up to a motion that there was not enough scientific evidence to back this claim.

But conservation group WWF says Australia insisted on a tougher wording of the motion, which caused whaling nations refuse to sign it.

Australia’s federal opposition environment spokesman Greg Hunt said environment minister Peter Garrett was doing more harm than good.

The original motion would have been a step towards ending whaling but Garrett had scuttled it, an “act of incompetence”, according to Hunt.

“Mr Garrett has further set back the push to end whaling once and for all,” he said.

But Garrett defended Australia’s resolution, saying it was the truth.

The original motion could have been used to justify so-called “scientific” whaling, he said.

“Australia’s resolution, passed with the support of around 85 per cent of member nations, puts the emphasis back on what the science is actually telling us, that whale numbers are not impacting on fish stocks,” he said.

Garrett said Australia was working hard to stop whaling and to redirect the International Whaling Commission’s focus to whale conservation.

It is understood that while the original motion said there was not enough evidence to support the “save the fish” argument, Australia’s motion gave less room to move, saying whales did not have an impact on fish numbers.