ACTIVISTS and the Coalition say a broken promise by the Federal Labor Government led three Australian anti-whaling protesters to board a Japanese whaling vessel.

West Australians Glen Pendlebury, Simon Peterffy and Geoffrey Tuxworth boarded the Shonan Maru 2 off Bunbury, WA, on January 7 and demanded the crew take them back to Australia.

The action was a futile attempt to divert the whaling fleet's security vessel from shadowing a Sea Shepherd anti-whaling boat.

In diplomatic talks, Japan agreed not to charge the men with trespass and allowed them to be picked up by an Australian customs boat, which brought them to the WA port of Albany on Monday.

Prime Minister Julia Gillard has said that exercise is likely to cost Australian taxpayers hundreds of thousands of dollars and warned protesters against similar actions.

But Mr Peterffy said the Forest Rescue trio would not have taken the action if the government had honoured its pledge to send vessels to the Southern Ocean to monitor the Japanese whaling fleet.

"The fault lies squarely with the Gillard government and the Labor Party," he told Sky News today.

"They promised us in the election that they would have a vessel down there policing our oceans against whalers.

"... If they had been down there, there would be no need for us to do our action, nor in fact for the Sea Shepherd to be down there defending our whales."

The Government previously has sent vessels to gather evidence for its International Court of Justice attempt to stop Japan's annual whale hunt and says further monitoring is not required.

Mr Peterffy said Japan should pay for getting the protesters home, since it was the captain of the Shonan Maru 2 who decided to take them down to the Southern Ocean.

"If there's any bill to be sent, it should be sent to the Japanese government," he said.

Opposition environment spokesman Greg Hunt said the government had ignored the Coalition's warnings that it needed a vessel to watch over the area.

"So it's not surprising whalers and protesters are both engaged in potentially illegal activity," Mr Hunt told Sky News.

He said the Government came to power pledging to have a customs vessel in the Southern Ocean and said it would reserve the right to board foreign whalers in its territorial waters and the Antarctic whale sanctuary.

"They broke their own word, they broke their own policy and now they are pretending it was never their policy."

Trade Minister Craig Emerson said the government was taking the proper legal course by going through the international court.

"That's the way to do it, not these sort of protest activities which are going to cost taxpayers hundreds of thousands of dollars," Dr Emerson said.

On his return, Mr Peterffy was arrested for outstanding fines totaling about $5000, which supporters later helped him pay.

He believes the arrest was "payback" from the Federal Government.

Originally published as Activists blame Labor for whaling clash