"The basic position is to go back to the Southern Ocean, and we are currently considering how to do this because we don't want to repeat the same situation" as earlier this year, Joji Morishita, deputy head of Japan's delegation to the International Whaling Commission, told AFP.

In February, Japan recalled its Antarctic fleet a month ahead of schedule with only one fifth of its planned catch, citing interference from Sea Shepherd's vessels.

The 89-nation IWC, roughly evenly split between pro- and anti-whaling nations, is meeting until Thursday.

Japan is one of a handful of nations that hunt the giant sea mammals despite a 1986 moratorium on killing whales.

"This year the attack was so extreme and violent we had no choice but to bring back our research vessels in order to avoid to a life-threatening situation for the crews," Morishita said.

"However, that does not mean that we have changed the policy about this research activity," he said.

Japan conducts whale hunting in the southern hemisphere for what it describes as "scientific research", setting self-determined quotas averaging about 1,000 whales each year over the last five years.

The killing is permissible under the IWC rules, but other nations and environmental groups condemn it as disguised commercial whaling.

Founder and head of Sea Shepherd Conservation Society, Paul Watson, told AFP on Tuesday that he would continue harassing Japanese whalers if they returned to the Antarctic sanctuary.

"If they go back to the Southern Ocean, then we go back the the Southern Ocean," he said.

Debate at the IWC's 63rd annual meeting, which closes on Thursday, has been dominated by whether or how to introduce the changes.

The new measure "sends a powerful signal that we are ready to move the IWC into the 21st century by improving its effectiveness and governance," said Richard Pullen, the head of Britain's delegation.

Under the old rules, members could pay subscription fees -- ranging from a few thousand to more than 100,000 dollars (euros) -- by cash or cheque, a practice that fuelled allegations of corruption.

Such payments must now be made by bank transfer, as is done in other international organisations.

The IWC was rocked last year by accusations in the British press that Japan used cash and development aid to "buy" votes from Caribbean and African nations.

Japan, which denied the charges, is one of three countries along with Norway and Iceland that practice large-scale whaling despite the moratorium.

Collectively, they take hundreds of the marine mammals each year. Smaller quotas are granted to other nations for traditional, indigenous whaling.

Wednesday's vote was adopted by consensus, a rare achievement in an organisation bedevilled by a rift over whaling quotas and finger-pointing between pro- and anti-whaling nations.

"I'd like this resolution not to be treated as as a win (victory) by some over others," Joji Morishita, deputy head of the Japanese delegation, pleaded just before the measure was passed.

Dropped from Britain's original proposal was a bid to strengthen the voice and access of non-governmental organisations in the IWC's proceedings.

"I know some of us would have liked to go further, particularly on the issue of observer and civil society participation," said Pullen.

"But negotiations mean compromise and the revised proposals we have in front of us reflect that."

Some NGOs nonetheless praised the outcome as significant progress.

"The final resolution is a step in the right direction for the forum," the International Fund for Animal Welfare (IFAW) said, calling it a "significant victory for whale conservation."