Greenpeace intends to shadow the fleet as it sails from Japan to Antarctic waters, while the more militant Sea Shepherd group plans to take direct action to disrupt the whale hunt.

Greenpeace’s ship was yesterday just outside Japanese territorial and hoping to find the whaling fleet as it steamed south to embark on the country’s biggest hunt since commercial whaling was banned.

The Japanese will, for the first time since a 1963 moratorium, aim to kill 50 protected humpback whales, a species popular with whale watchers because of its spectacular acrobatic behaviour and haunting ’songs’. The whales will be harpooned, ensuring a slow and agonizing death. It will also harvest 935 minke whales and 50 fin whales.

Australians are particularly concerned about the fate of what is believed to be the world’s only completely white humpback whale, nicknamed Migaloo, which has become a celebrity for his annual migration along the country’s east coast.

“It’s a large ocean, but we’re going to track them down,” Greenpeace expedition member Dave Walsh said on board the Esperanza. “They’re playing a little hard to get.”

On Sunday, the Japanese expedition was farewelled on its five-month voyage from the port of Shimonoseki, where families waved flags emblazoned with smiling whales and a brass band played “Popeye the Sailor Man.”

The good cheer will not last long - the head of the fleet described the campaigners as “violent environmental terrorists.”

During the last whaling season, Sea Shepherd said it would attack the Japanese fleet with a ship fitted with a bulldozer-type blade nicknamed the “can opener”.

Sea Shepherd’s president, Paul Watson, threatened to use the ram to give the Japanese fleet’s factory ship, Nissin Maru, a “steel enema”.

Flying a Jolly Roger pirate flag, the group attacked the whalers with nail guns and foul-smelling acid after a five-week cat and mouse chase in the Southern Ocean.

This year Sea Shepherd has threatened to deploy “new equipment for intervention” when it sets out for Antarctic waters from Melbourne next week as part of ‘Operation Migaloo’.

Capt Watson has called on Australia and New Zealand to “defend Anzac honour by kicking their ruthless whale killing arses out of the Southern Oceans Whale Sanctuary.”

But Sean McCormack, spokesman for the US State Department, urged anti-whaling groups to use “restraint and measured approaches” in their protests.

“The sinking or damaging of a vessel in this area could have catastrophic consequences for the crews involved, the environment, and indeed the living resources all parties cherish in the region,” Mr McCormack said.

Assuming the hunt was, as Japan contended, for scientific purposes, non-lethal methods exist that could achieve the same goals, he said.

“We call on Japan to refrain from conducting this year’s hunt, especially with respect to humpback and fin whales,” he said.

New Zealand’s prime minister, Helen Clark, accused the Japanese of “deception” in arguing that they were killing whales for scientific research.

“We don’t like the Japanese whaling fleet being down there at all,” she said.

Britain is considering making a “high-level diplomatic protest” to Japan, the Department for Environment, Food and Rural Affairs said. In Australia the opposition Labour party, tipped to win power at a general election on Saturday, said it was time to “rattle the cage”. “It’s unacceptable that it’s not only going on, but getting worse,” said Labour’s foreign affairs spokesman, Robert McClelland.

Labour has pledged that, if elected, it will use the Australian military to monitor the whaling fleet and compile evidence which could be used in international courts to end the hunting.

Prime Minister John Howard said that while he disagreed with whaling, he opposed bringing in the military.

“What, is he going to shoot them?” he asked. “Mr McClelland knows darn well that what he is suggesting is an empty gesture, that what we should be doing is continuing to pursue diplomatically, and with whatever legal mechanisms are available to us, this issue.”

Japan says it needs to kill whales to conduct research on their age, breeding habits and feeding patterns.

Environmental groups say that is rubbish, that valuable research can be conducted without harming the animals. They accuse Japan of using science as a cover for commercial whaling.

An International Whaling Commission moratorium on commercial whaling took effect in 1986, but Japan has killed almost 10,500 mostly minke and Bryde’s whales under “research permits” since then.

Whale facts

Humpback whales can reach 50ft long and weigh 40 tonnes.

The American Cetacean Society estimates the humpback population has recovered from near extinction to about 30,000-40,000.

The species is listed as “vulnerable” by the World Conservation Union.

Despite the supposed scientific aim of the hunt, whale meat ends up in Japanese schools, old people’s homes, supermarkets and restaurants.

Japan argues that eating whale meat is a cultural tradition.

Its fleet will roam the Southern Ocean in search of whales between now and April.

Some of the whales are likely to be harpooned within an Australian-declared whale sanctuary, off the Australian Antarctic Territory, which Tokyo refuses to recognize.

Last year the Japanese caught around 500 minkes but the hunting season was curtailed after a fire broke out on the main factory ship, killing a crewman.