SYDNEY, Jan 7, 2009 (AFP) - Anti-whaling campaigners on Wednesday denied charges that they had harassed Japanese whalers searching for a missing crewman in Antarctic waters and said they were simply trying to help.

"We were there definitely to assist them," said Paul Watson, captain of the Sea Shepherd Conservation Society vessel the Steve Irwin.

"I think it's very impolite and very unfair to make these accusations that we were harassing them when they knew that in fact we were not," Watson told AFP by satellite phone from on board the ship.

Watson announced on Saturday the Steve Irwin was returning to port to refuel after two weeks tailing the Japanese whaling fleet through the Southern Ocean.

But Japan's Institute of Cetacean Research (ICR), a government-backed whaling body, accused the vessel of latching onto a distress signal to find the fleet again and hamper efforts to rescue a seaman lost overboard.

In a joint statement with the fleet's parent company Kyodo Senpaku Kaisha, the ICR on Wednesday accused the Steve Irwin of cruising with its lights off and trying to disrupt the search.

"Despite our loss and that we are in the midst of a search, the Dutch (registered) vessel has begun to disrupt the navigation of our vessels in the search," said Kyodo Senpaku Kaisha president Kazuo Yamamura.

"There is a distinctly uncaring nature about Sea Shepherd people in that they are prepared to disrupt the search for a missing seaman for their own ends."

The missing crew member was believed to have fallen overboard in the icy Antarctic Ocean waters after he failed to report for duty, the fleet's operator said Tuesday.

An international moratorium on commercial whaling was imposed in 1986 but Japan kills hundreds of whales a year in the name of research.

It makes no secret of the fact that the meat ends up on dinner tables and says whaling is a cultural tradition.

For the past four years Watson has led a Sea Shepherd vessel to find, track and attempt to impede the whaling ships during their hunting season, the Southern Hemisphere summer.

Watson told AFP that the Steve Irwin was now en route to the southern Australian city of Hobart, where he expected to dock and refuel on January 15.

Japan said Tuesday it would ask Australia to ban the vessel from refuelling at its ports.

"We are seeking every possible way for Australia, New Zealand and other countries concerned to cooperate in preventing their sabotage," said Shigeki Takaya, an official with Japan's Fisheries Agency.

"One effective measure is to ask the countries to prevent the ship from entering their ports for refuelling or to prevent it from departing," Takaya told AFP.

Australia's acting prime minister Julia Gillard said in response that "usual" procedures and laws would apply to any request from the Steve Irwin to berth.

While she noted that the vessel had previously been allowed to enter Australian ports, most recently in December, Gillard, acting premier while Prime Minister Kevin Rudd takes a holiday, warned against dangerous acts of
protest.

"Australia respects the right to peaceful protest at sea, but condemns dangerous, violent or illegal protest activities, including any activity that may jeopardise safety at sea," Gillard said in a statement.

Australia strongly opposes Japan's annual whale hunt, and the issue is an irritant in relations between the longtime allies.

Watson said Japan's request to Canberra to ban his ship from Australian ports showed "we're hurting them, we're hurting their profits.

"We have not committed a crime, we have not damaged any property and we haven't hurt anybody, so there's no cause for either Australia or New Zealand to bar us from entry into their ports."