Greg Hunt

Plans to send an A319 Customs aircraft to the Southern Ocean instead of the originally promised ship: Environment Minister Greg Hunt. Photo: Alex Ellinghausen

Anti-whaling activists have slammed the federal government for breaking an election promise to send a ship to monitor Japanese whaling in the Southern Ocean.

Environment Minister Greg Hunt said on Sunday that an A319 aircraft staffed by Customs officials would be sent instead.

Jeff Hansen

Unhappy: Sea Shepherd director Jeff Hansen says a plane is useless for monitoring whalers. Photo: Andrew Darby

Sea Shepherd Australian director Jeff Hansen, whose conservation society last week sent three vessels from Melbourne and Hobart to intercept the Japanese whaling fleet, said a plane was of no use.

''It's a broken promise,'' Mr Hansen said. ''The promise was - to the whales and to the Australian public - to send a vessel. Sending a plane is really a waste of taxpayers' money.''

The organisation's chairman, Dr Bob Brown, said on Monday that it was a ''plane cop out''.

''They’re going to fly over at a height seeing what we all know is happening down there, and that’s the bloody and illegal destruction of Australian whales,'' he said.

Dr Brown said the $150 million Oceanic Protector, which was patrolling at Christmas Island thousands of nautical miles away, should be on the job.

''The government has got it to turn back the (asylum seeker) boats, but not the Japanese whaling boats,'' he said.

He said the minister ''who should stand up for Australia's rights'' had caved under pressure to avoid offend Japan during free-trade negotiations.

''That plane is not going to prevent anything. Who are they going to call, and from where, and how long is it going to take to get there?'' Dr Brown said.

Speaking in Frankston, Victoria, on Sunday, Mr Hunt said the purpose of using a plane was threefold: to observe any whaling, to ensure there was ''a record and a chronicle'' of any conflict between whalers and conservationists and to show both sides that they were being observed by an independent party so ''they have to behave properly''.

''Our promise was for a Customs monitoring mission,'' Mr Hunt said. ''We are delivering a mission which, on the advice of Customs, has greater flexibility, greater range.

''Not only are we fulfilling the promise, we're exceeding it because what it does is it allows us to cover not just one vessel but multiple vessels in a rapid period of time.''

Asked if the ship Ocean Protector, purpose-built to patrol the Southern Ocean, would continue to be used to ferry asylum seekers and patrol Christmas Island, Mr Hunt said: ''I'll leave the use of Customs assets to the Customs bureau.''

But Mr Hansen said: ''The Ocean Protector, that was purpose-built for the Southern Ocean environment and it's up there in a tropical environment basically used as a glorified taxi. Hunt was [previously] very much adamant saying a vessel needs to be down there.''

Sea Shepherd Australia's chairman Bob Brown says the Abbott government has broken a core election promise to send a vessel to the Southern Ocean this whaling season, effectively turning a blind eye on the slaughter of these great creatures.

Dr Brown says Sea Shepherd Australia is now left alone to do the government's role of enforcing Australian and international law in the Antarctic region.

Greens senator Peter Whish-Wilson called on Mr Hunt to resign.