Wellington, May 24 NZPA - Anti-whaling activist Peter Bethune will have consulate support throughout his trial in Japan this week, along with his own team of senior lawyers, but the New Zealand Government will otherwise stand back from the court process.

Mr Bethune, 42, was arrested after boarding Japanese whaling fleet vessel the Shonan Maru 2, hoping to make a citizen's arrest of its captain following a collision between it and his anti-whaling speed boat, Ady Gil, in January.

The Ady Gil sank after being broken in two pieces and Mr Bethune alleges the blame lies with the Japanese boat and its captain.

He was detained once on board before being taken to Japan and charged with trespass, causing injury, vandalism, carrying a knife and obstructing commercial activities.

Prime Minister John Key told reporters today Mr Bethune was getting as much support from the New Zealand consulate as could be provided.

"But it's worth noting that I can't get involved in a prosecution in another country any more than I can get involved in a prosecution in New Zealand. What I can do is make sure the person is being treated fairly," he said.

A consulate official spent an hour with Mr Bethune last Wednesday and there would also be an official presence throughout the trial, which starts on Thursday and could be over in three days.

"I'm advised the embassy and his lawyers can have access at any time," Mr Key said. "We will continue to monitor the situation closely."

Some opposition MPs and anti-whaling activists say the Government has not done enough to try to secure Mr Bethune's release leading up to the trial, but Mr Key has maintained it is wrong to interfere in the Japanese justice system.

The offending leaves Mr Bethune open to a prison sentence and he was reported in the Sunday Star-Times at the weekend as saying his chances of getting off lightly were almost nil.

An investigation into the collision between the two boats is being conducted by Maritime NZ.