Australia said Wednesday it had rejected a call from Japan to provide more security for its whaling fleet in Antarctic waters, the site of violent clashes with animal rights activists in previous years.

The Japanese fleet left port Tuesday on the country's annual hunt and activists with the militant Sea Shepherd Conservation Society, who plan to harass the whalers, said they were preparing to join them within days.

But Environment Minister Tony Burke said Canberra had no plans to send a navy or Customs vessel to monitor events in the remote Southern Ocean, despite a Japanese call for action at an International Whaling Commission meeting.

"What Japan was asking of us was to provide a higher level of protection for their vessels simply because they are involved in whaling. There is no way that we could countenance something like that," Burke told the ABC.

US-based Sea Shepherd has also asked Australia to send a ship south in case a high-seas confrontation develops during their months-long pursuit of the whalers in the harsh environment.

"That is one of the reasons I asked Australia to send a vessel down -- to keep the peace -- but they refused," Sea Shepherd founder Paul Watson told Australian news agency AAP.

Sea Shepherd, which claimed a victory in its fight against the whalers when Japan cut short its last hunting season by one month after taking only a fifth of its planned catch, said it still planned to frustrate the harpooners.

In previous years the activists have lobbed stink bombs onto the decks of the Japanese fleet, while vessels from both sides have repeatedly clashed, including in January 2010 when a collision destroyed a Sea Shepherd trimaran.

Australia last despatched an armed Customs ship, the Oceanic Viking, to the Southern Ocean in early 2008 to gather evidence to use against Japan in a legal challenge to the hunt at the International Court of Justice.

That patrol ship ended up collecting two anti-whaling activists from the Japanese vessel Yushin Maru No.2 which they boarded under cover of darkness after a risky jetski journey.

Australian Greens leader Bob Brown said the government would be held responsible if a confrontation between the whalers and the conservationists ended in violence.

Japan says its whaling is for scientific purposes but Burke said Australia did not "buy for one minute this argument".

"You don't travel from one side of the globe to the other to harpoon whales and chop them up in the name of science," he said.