A "problematic and ambitious" Japanese proposal to end the moratorium on commercial whaling will be strongly opposed by Australia at the International Whaling Commission in Brazil next week.

The International Whaling Commission paused whaling more than three decades ago after concerns about depleting stocks.

Despite being commission members, Japan, Iceland and Norway all continue to hunt whales, with Japan arguing the practice is for research.

Australia has long opposed commercial whaling and in 2010 the Rudd government challenged Japan's illegal whaling practices in the International Court of Justice.

In 2014, the court concluded the country's whaling program was for reasons other than scientific study and ruled all permits were to be revoked.

Dr Gales says a return to commercial whaling could pose a major threat to the species. ( ABC News )

According to the World Wildlife Fund, Japanese whalers have killed more than 50 minke whales in a protected Antarctic area this year.

Nick Gales, who is about to retire as director of the Australian Antarctic Division, is Australia's commissioner to the International Whaling Commission.

He said for a long time Japan had effectively used a loophole to continue whaling.

"Japan has brought forward a very ambitious and very problematic proposal essentially to start the move to end the moratorium on commercial whaling," Dr Gales said.

"What they're doing now is pushing to cease using that loophole and actually return to a larger scale commercial operation."

He said a return to the days of commercial whaling could pose a major threat to the species.

"With the populations of whales back in the days of industrial whaling, the major single threat they faced was whaling. Today, with climate change, fisheries interactions and bycatch noise in the ocean, there are many other threats.

Japan wants to return to a large-scale commercial operation. ( Supplied: Australian Customs )

"To add commercial whaling to that now, at a time when populations are really only starting to recover, in Australia's view would be a really unwise step."

Mr Gales said "Japan brought the proposal forward very rapidly", which took everyone by surprise but he was hopeful it would not succeed.

"I think we have the numbers to ensure that Japan can't progress its proposal," he said.

While he said it was difficult to see how it would play out, Australia would stand by its convictions.

"Australia will make very clear that it will hold to, and prosecute, its very strong policy of opposing all forms of commercial whaling," he said.

"And will really do what it can to prevent Japan … in any way starting a process that might see an end to the moratorium and a recommencement of commercial whaling."

Whales suffer prolonged deaths: Gales

Dr Gales believes the Japanese proposal will fail. ( Supplied: Japan Institute Cetacean Research )

Population pressures was not the sole concern, with Dr Gales highlighting the time it can take for whales to die.

He said killing such a large animal in a humane way was very difficult.

"Imagine being on the high seas and trying to kill a really enormous animal. It's very difficult even with the modern equipment used for whaling," he said.

"While some proportion of the whales will be killed very quickly, quite a large proportion can take many minutes, up to half an hour or so to die.

"If it was sheep or cattle, those kind of statistics would be seen as entirely unacceptable, and so they should be with whaling."

Attempts were made to contact the Japanese Government's Institute of Cetacean Research for comment.