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"Almost pathetic" is one reaction to the Government's handling of the anti-whaling protester being held on board a Japanese ship.

Peter Bethune boarded the whaling vessel Shonan Maru 2 in the early hours of Sunday to make what fellow protesters describe as a citizen's arrest of its captain.

The New Zealand activist alleges the captain rammed and sunk his $3 million anti-whaling boat the Ady Gil last month and attempted to murder his crew.

Mr Bethune, who is part of the Sea Shepherd Conservation Society, is believed to be held on the Shonan Maru 2 and it is possible he will have stay on board till the ship returns to Japan. It is not clear what will happen to him then.

Captain Paul Watson, whose ship the Steve Irwin is following the Shonan Maru 2, told the Herald last night it had been 30 hours since he had heard from Mr Bethune and he was concerned by Japanese reports that he had a cut hand.

Yesterday there were growing calls for the Government to intervene. There was also criticism from the Sea Shepherd Conservation Society about the Government's alleged lack of interest in Mr Bethune's situation.

"I can't think of a single case where a vessel has been deliberately rammed, destroyed and sunk by another vessel and the country of registry - which for the Ady Gil is New Zealand - has said nothing," said Mr Watson.

"It is almost pathetic how the Australian and New Zealand Governments roll before the Japanese."

Foreign Minister Murray McCully said yesterday he had met the Japanese Ambassador and told him New Zealand wanted to offer consular assistance to Mr Bethune. He was confident efforts would be made to ensure that happened.

Mr McCully said he was not going to discuss the logic behind Mr Bethune's actions but suggested the activist would have been fully aware of the outcome.

"I think he is being detained precisely in accordance with his own wishes. My understanding is that he went on board to make a point, knowing that there would be some consequences that flowed from it, and that he is not only not seeking to be removed, but is refusing to be removed at this stage."

Prime Minister John Key said while Mr Bethune felt strongly about whaling, his actions had presented significant risks.

"There has got to be a better way through this and would prefer that calm heads prevail."

Labour's Foreign Affairs spokesman, Chris Carter, said the Government must take a more active role.

"To have Prime Minister Key and Foreign Minister McCully essentially washing their hands over Pete Bethune's fate is simply not acceptable."