"I think any sort of activity or any sort of suggestion that ship will be interfered with in any way when it gets to any Australian port would jeopardise that man's life," said Environment Minister Ian Campbell.

Two Greenpeace ships located and had a confrontation with the Japanese whaling fleet in the Southern Ocean off the coast of Antarctica south of Tasmania on Wednesday.

One of the environmental group's boats, the Esperanza, was nudged aside while blocking the access of a whaler trying to unload dead minke whales onto the factory ship, Greenpeace said in a statement.

Japan's fisheries agency condemned Greenpeace's actions. "It seems like piracy," an agency spokesman told Australian national radio.

"I hope that Greenpeace refrains from such kind of dangerous actions immediately."

Campbell said that while the Australian government opposed commercial whaling, Greenpeace's actions could be counterproductive and urged activists to respect the law of the sea.

"The fundamental law is that you avoid collision and you avoid bringing ships, and the personnel on the ships, into a position where they can endanger human life," he said.

Prime Minister John Howard told a news conference later that he had raised the whaling issue with Japanese Prime Minister Junichiro Koizumi during a recent meeting.

"I did not lose the opportunity of telling him of my continued opposition to Japan's position on whaling," he said.

"However I do not support action which endangers lives or breaks the law."

Japan says it conducts whale hunts for scientific research, but Greenpeace expedition leader Shane Rattenbury said that "once the whales have been measured and weighed by the 'scientists' the onboard butchers get to work and the whales are cut up and boxed for market.

"This is all about money and not science."

Despite international protests, Japan has this year more than doubled its planned catch of minke whales to 935 and added 10 endangered fin whales.

Greenpeace said one of the fleet of five Japanese ships would arrive in Hobart in Tasmania on December 24 to deliver a crew member with appendicitis to hospital, and urged Australia to prevent it from returning to whaling.

"The Australian government does have control over port authorities and we believe it does have the possibility to refuse to allow the ship to be refuelled," said Greenpeace CEO Steve Shallhorn.

Meanwhile, Rattenbury said the Greenpeace activists would continue to harass the whaling fleet.

"As soon as the whale is in sight and the catcher's chasing it we will immediately put ourselves and our boats between the whale and the harpoon to confuse the harpooner's line of sight and to provide the whale with an opportunity to escape and to shield the whale from the harpoon," he said.

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