Australia has expressed its alarm as support grows internationally for a pact to legalise whaling.

New Zealand has backed the compromise pact, which would lift the current ban on commercial whaling while reducing the number of whales killed by Japan under the guise of "research".

NZ had been one of Australia's staunchest allies in the fight against Antarctic whaling.

But now the country's whaling commissioner, Sir Geoffrey Palmer, says he'll support the compromise proposal at the next meeting of the International Whaling Commission (IWC) in June, the ABC reports.

Currently, commercial whaling is banned but countries can hunt whales in the name of science. Up to 1900 are killed each year.