The call by Environment Minister Ian Campbell came after a Japanese harpoon narrowly missed a Greenpeace dinghy trying to protect a minke whale on Saturday, with the rope knocking one activist into the icy water.

It was the latest in a series of dangerous incidents since two Greenpeace ships began harassing a Japanese whaling fleet several weeks ago, launching small inflatable boats to get between the harpooners and their targets.

"I don't think people are going to have respect for tactics that are going to put human life at risk," Campbell told national radio. "We don't want to bring the whole cause of whale conservation into disrepute.

"They both need to understand that they have to respect human life. Greenpeace has said that they're going to do that, so do the Japanese fishing authorities -- they need to walk that talk."

In Tokyo, the government defended its whaling as within international rules.

"I understand that Japan's research whaling follows international rules and is done for the purpose of research on whales' ecosystem," Chief Cabinet Secretary Shinzo Abe, the government spokesman, told reporters.

Abe declined to comment directly on the latest clash, saying he did not know the details of the incident.

The International Whaling Commission imposed a moratorium on commercial whaling in 1986 but Japan has continued hunting for what it calls scientific research.

Japan, however, makes no secret of the fact that the meat from the hunt winds up on dinner plates.

Greenpeace spokesman Shane Rattenbury said the activists were aware of the dangers involved in their protests.

"The aggression shown over the weekend is a warning to us and we need to think hard about what our tactics are from here," he told Australian radio. "We've got quite a few tricks up our sleeve yet.

"For them to now be taking shots that are flying straight over the inflatable boat suggests that they are under pressure," he said.

A little over a week ago the Greenpeace ship Arctic Sunrise collided with the Japanese whale processing ship Nisshun Maru and each side accused the other of responsibility for the crash.

Australia has refused to intervene in the whale hunt in its self-proclaimed whale sanctuary in the Southern Ocean, but Campbell said the government had made its views on whale conservation clear.

"I think what is important is that we maintain our focus on the main game," he said.

"And that is that whaling will come to an end when the people of Norway and the people of Japan tell their governments unequivocally that the slaughter of whales needs to come to an end."

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