Tokyo - Japan is considering upgrading its ageing lead whaling ship, a fisheries official said Wednesday, as the prime minister vowed to continue the country's controversial Antarctic hunts despite international protests.

The Fisheries Agency has requested 100 million yen ($910,000) in the national budget for a study into the future of commercial whaling, an agency official told AFP, including the fate of the 30-year-old Nisshin Maru, the lead vessel of Japan's whaling flotilla.

"That study will include discussions on what to do with the Nisshin Maru - if its life should be extended (by repairs), or should be replaced with a used ship or a new ship, among other ideas," Takato Maki said.

Japan is a signatory to the International Whaling Commission (IWC) moratorium on hunting, but exploits a loophole that allows whales to be killed in the name of scientific research.

Tokyo says slaughter is necessary for in-depth knowledge of whale behaviour and biology, but it makes no secret of the fact that whales killed in the hunts often end up on dinner plates.

On Wednesday, Prime Minister Shinzo Abe confirmed his government's commitment to an eventual resumption of commercial whaling.

"We will pursue all possibilities in order to resume commercial whaling, including opportunities at the September meeting of the IWC," he told parliament, when asked to comment on the nation's policy.

He said he favoured a continuation of Japan's traditional use of whale meat, fat, and baleen "in a sustainable manner based on scientific evidence, just like other marine resources." In 2014, the UN International Court of Justice ordered Tokyo to end its regular hunt in Antarctic waters, saying the project did not meet conventional scientific standards.

Japan cancelled its 2014-15 hunt, only to resume it the following season under a new programme that it said now had genuine scientific value.

In December, the European Union and 12 other nations condemned Japan's Antarctic whaling programme.

Tokyo says it is trying to prove the whale population is large enough to sustain a return to commercial hunting for a traditional source of food.

In the latest mission, five Japanese vessels including the Nisshin Maru left port in November for the four-month expedition, expecting to kill 333 minke whales.

Japanese whalers have in the past clashed at sea with animal rights campaigners, particularly the Sea Shepherd activist group.

Japan's mass-circulation Yomiuri daily said last week the fisheries agency was planning to buy a new ship or refit one in part to help its whalers evade anti-whaling activists at sea.