The former leader of Australia's parliamentary Green Party Bob Brown will spearhead Sea Shepherd Society's next anti-whaling protest in the Southern Ocean.
Legal action has forced the Sea Shepherd founder Paul Watson to resign as president of the US chapter after more than three decades at the helm.
Mr Brown will take on the role of directing the organisation's fight against Japanese whalers, the ABC reports.
The move was announced in Hobart this morning where the organisation's fourth vessel, the Sam Simon, has been delayed by forecast storm-force winds.
Watson is in the Southern Ocean, waiting for the Japanese whaling fleet to start their annual whale hunt.
He has also resigned as the society's Australian president.
Director Jeff Hansen says it is a response to a US court ruling that personally named Watson and limited the anti-whaling activities.
"It shows the calibre of Paul's selflessness," he said.
Last month, an appeals court in the United States issued an injunction, ordering the anti-whaling protesters to stay at least 450 metres from the Japanese fleet.
The injunction followed court action by the Japanese Institute of Cetacean Research which conducts whaling in the Southern Ocean.
The institute said it was part of a strategy to stop Sea Shepherd.
Mr Brown says it is an honour to head the campaign.
The Sam Simon is expected to leave Hobart in the next day few days.