A lawyer for Japan's whalers claims the Australian Sea Shepherd ship, Brigitte Bardot, has breached a US court restraining order in the Southern Ocean.

In the first test of the conservation group's shift of its anti-whaling campaign to Australian hands, the lawyer claims the Bardot closed on the harpoon ship, Yushin Maru No. 3.

The US Ninth Circuit appeals court imposed an injunction on the Washington State-based Sea Shepherd Conservation Society (SSCS), restraining its ships from attacking the whaling fleet, or approaching within 500 yards (457 metres).

A lawyer for the Institute of Cetacean Research in Seattle, John Neupert, said the group's fast reconnaissance boat approached from behind Yushin Maru No. 3 and came within 20.25 yards (18.5 metres) of the harpoon ship on January 29.

"This is a clear violation of the injunction," Mr Neupert said in his letter to SSCS lawyer Charles Moure.