An Australian court on Tuesday ruled Japanese whaling in the Antarctic illegal but admitted it had no power to stop it.

The Federal Court, in a hearing brought by the Humane Society International, declared the Japanese in contravention of Australian environment protection legislation because they were killing and injuring minke and fin whales in the Australian whale sanctuary in the Southern Ocean.

Justice James Alsop noted that Japan doesn't recognize the whale sanctuary and society was powerless to enforce the injunction he granted.

Environment Minister Peter Garrett skirted around the question of whether the government would seek to enforce the injunction and try to stop the Japanese.

"We will have an adequate and comprehensive monitoring in place," Garrett told reporters in Canberra. "It will enable us to have every good opportunity to take material and information in the event that we are able to take a case forward, which is what our intention is."

At the weekend, the environmental group Greenpeace met with success in its 10-day effort to locate Japan's whaling fleet, which took flight.

"For the amount of time that they run, they are not whaling," Greenpeace whales project leader Sara Holden said in a statement issued from the ship Esperanza. "Our primary objective is to stop the Japanese fleet from whaling in the Southern Ocean whale sanctuary."

The four-vessel fleet left Japan in November with the intention of returning with 935 minke whales and 50 fin whales. Initially, 50 humpbacks were to be taken as well, but this part of the catch is in abeyance after Australia and New Zealand led an international protest.

The new Australian government led by Prime Minister Kevin Rudd has been accused of talking tough against whaling but doing little to stop it. An Australian ship left Perth last week on a 20-day mission to monitor the Japanese.

The Oceanic Viking with 30 Customs officers on board intends to gather video evidence for a possible international court action against the Japanese government-sponsored whaling.

Opposition environment spokesman Greg Hunt urged Rudd to deliver on Labor Party promises and wind up pressure on the Japanese government to stop its annual harvest.

When it was in opposition, Labor had castigated then-prime minister John Howard for not succeeding in pressuring Tokyo to abandon whaling, which it calls "scientific whaling."

Research whaling is allowed under an international whaling moratorium, but critics of Japan said no research is involved in its hunt.