Japan said Tuesday it has cut its Antarctic whale-catch quota by two-thirds in a move it hopes will convince international opponents it is conducting real science, not hiding a commercial hunt behind a veneer of research.

The International Court of Justice -- the highest court of the United Nations -- ruled in March that Japan was abusing a scientific exemption set out in the 1986 moratorium on whaling.

The court said the controversial programme, which sees taxpayer-subsidised Japanese boats harpooning the huge mammals and then selling their meat, supposedly as a by-product, was a commercial hunt masquerading as research.

Judges said any nation that wanted to avail itself of the scientific exemption must show why it was necessary to kill whales as part of its study.

Japan cancelled its 2014-15 Antarctic hunt after the ruling, but said it intends to resume "research whaling" in 2015-16.

"We will explain the new plan sincerely so as to gain understanding from each country," Minister of Agriculture, Forestry and Fisheries Koya Nishikawa told reporters.

In the new plan submitted to the International Whaling Commission (IWC) and its Scientific Committee, Japan has set a new annual target of 333 minke whales, down from some 900 under the previous programme, the government said in a statement.

This level of catch is "necessary" to obtain information on the age of the population, detail Japan says it needs to allow the setting of "safe levels of catch limits" and to ensure sustainability.

Tokyo also defined the research period as 12 years from fiscal 2015 in response to the court's criticism of the programme's open-ended nature.

Japan killed 251 minke whales in the Antarctic in the 2013-14 season and 103 the previous year, far below its target because of action by activist group Sea Shepherd.

Tokyo also conducts hunts in the name of science in the Northwest Pacific, where it killed 132 whales in 2013, and off the Japanese coast, where it caught 92.

The world's whaling watchdog the IWC agreed this year to toughen scrutiny of Atlantic hunts, but rejected a bid to expand protection in the South Atlantic, as it struggles to balance traditional hunting claims with conservation.

Conservationist group Greenpeace said fiddling with the figures did nothing to address the fundamental lack of science.

"Even though the new programme stresses the point that it added nonlethal research, the essence of 'research aimed at maintaining whaling' has not changed from the previous programme," Greenpeace Japan said in a statement.

"People in Japan and around the world know the purpose of the whaling programme is not research, but a taxpayer-funded subsidy for the whaling industry," it continued.

"This programme is not only a waste of money, but also risks discrediting global trust in real Japanese science."

"If it is really interested in science, Japan should retract the new plan and conduct comprehensive research on ecosystems in the Antarctic in cooperation with other countries," Greenpeace said.