A bitter feud has broken out between anti-whaling activist Pete Bethune and the conservation group Sea Shepherd, which broke ties with him yesterday.

Mr Bethune, 45, says he has resigned from the Sea Shepherd Conservation Society, citing the alleged dishonesty of its senior members as his reason.

The Hamilton-born activist has been embroiled in a war of words with Sea Shepherd founder and captain Paul Watson over his trial in Japan in June and incidents leading up to it.

Mr Watson has accused him of "betraying" the organisation by giving false testimony to the Japanese.

In emails which have been republished online, Mr Bethune said he was asked by Sea Shepherd to scuttle the Ady Gil, which he skippered, after its collision with Japanese whaling vessel Shonan Maru No 2.

Mr Bethune had felt the $1.5 million boat was salvageable. He said Mr Watson had falsely told Sea Shepherd supporters and journalists it had sunk while being towed to port.

"It was a totally dishonest thing to do and as a conservation group, the order is a total breach of ethics."

He said he still "loved" Sea Shepherd, but the organisation had become "morally bankrupt" and needed to be more honest with its supporters.

Japanese police arrested Mr Bethune after he boarded the Shonan Maru in the Antarctic while seeking compensation for the loss of his boat.

He was held for three months in Tokyo then sentenced to two years in jail, the sentence suspended for five years.

Sea Shepherd's international division yesterday issued a statement saying Mr Bethune would no longer be associated with the organisation or its campaigns.

The organisation expelled him during his trial, but later said that was a strategy to encourage a more lenient sentence from the Japanese court.

Mr Watson accused Mr Bethune of making a false statement to the Japanese police which meant he was now "wanted" by Japanese authorities.

A transcript of Mr Bethune's statement to the Japanese said he had been instructed to board the boat by Mr Watson.

Mr Watson said he was "shocked and deeply disappointed" because he understood Mr Bethune would take full responsibility.

Mr Watson has since been stopped and questioned at United States border control before being released.

Mr Bethune told the Herald yesterday that he was following the advice of his lawyers in making the statement.

"I made an error of judgment, and I apologise to Paul for that. He has been handcuffed once. If you're an activist that's not a big deal. I did five months."

Conservationists yesterday said the tussle undermined the real issue - protesting against whaling. The next whaling season in the Southern Ocean begins in November-December.

United States businessman Ady Gil, who donated the boat which bore his name to Sea Shepherd, backed Mr Bethune's resignation.

WHAT SEA SHEPHERD SAYS
* The Ady Gil sank while being towed to port after a collision with the Shonan Maru No 2.
* Bethune broke Sea Shepherd's non-violence policy by bringing a bow and arrow on board the Ady Gil.
* Bethune's initial expulsion from Sea Shepherd during his Japanese trial was a ploy to encourage a more lenient sentence.
* Bethune's false testimony to Japanese authorities reportedly led to the issue of an arrest warrant for Sea Shepherd founder Paul Watson and his addition to Interpol's "Blue List".
* Sea Shepherd supported Bethune as an anti-whaling activist but wished to "quietly" dissociate itself from him.

WHAT PETE BETHUNE SAYS
* He was asked by Sea Shepherd to scuttle his boat after the collision.
* He was given permission to take the bow and arrow on board, then criticised by Sea Shepherd when arrows were found by the Japanese.
* His expulsion from Sea Shepherd hurt his case in court.
* His testimony followed legal instruction.
* He still "loved" Sea Shepherd but felt the organisation was too dishonest for him to stay.