The Greens say the Government has failed to support a New Zealand citizen who is at the peril of Japanese political interest in whaling.
Peter Bethune went on trial today in Japan after he was detained by whalers more than three months ago when he boarded the Shonan Maru II, the security ship of the Japanese whaling fleet, during its annual cull of the sea mammals.
Mr Bethune was working for the US-based Sea Shepherd Conservation Society, on its the Ady Gil trimaran - formerly the record-setting Earthrace - when it and the Japanese whaling fleet's security ship the Shonan Maru II collided in January.
Three of the charges he stood trial for stem from his doomed bid to later make a "citizen's arrest" of the Japanese captain, for what he said was the attempted murder of the Ady Gil's six crew.
Green Party co-leader Metiria Turei said Maritime New Zealand was conducting an investigation of the collision of the Ady Gill and Shonan Maru and was waiting for GPS data from the Japanese.
The New Zealand Government should be supporting the Maritime NZ investigation but did "not appear to be doing anything" to get the information.
It was possible the Japanese ship was responsible for ramming the Ady Gill which would make Mr Bethune's actions legal, Mrs Turei said.
"If the Maritime New Zealand investigation shows the Japanese vessel was at fault then this has been a serious mistrial and the New Zealand Government has been implicit (sic) in that mistrial.
"I'm very concerned that someone who was protecting the New Zealand interest, because the Government was refusing to, is going to be sacrificed to Japanese political interest in whaling, he should not be going to jail, he should not be on trial."
Prime Minister John Key said the Government was requesting advice from the Japanese and trying, through Maritime NZ, to get the best information.
He said he did not know whether details about the collision should be used in Mr Bethune's defence.
"I honestly haven't had a look through the depositions and what case they are making but in the end we are trying to give Peter Bethune whatever support we can, not withstanding he is being tried under the Japanese jurisdiction and we can't prevent that but if we are in a position to help him and give him any information we certainly would not withhold that."
Meanwhile, Labour was disappointed the Government would not allow its notice of motion calling on Japan to cooperate with the Maritime NZ investigation.
Its independent assessment was only possible with help from the Japanese authorities, party spokesman Chris Carter said.
It was another example of National "washing their hands of the fate" of Mr Bethune.