A dead baby minke and adult whale are hauled up the slipway of a whaler in this picture supplied by the Australian Customs Service.

A dead baby minke and adult whale are hauled up the slipway of a whaler in this picture supplied by the Australian Customs Service.

Disturbing footage of a slaughtered baby minke being hauled up the slipway of a whaler alongside the carcass of its mother will be used against Japan in international legal action being planned by the Australian Government.

The footage of the dead mother and calf, estimated to be less than 12 months old, was released after demands by anti-whaling activists for the publication of incriminating pictures taken by the Australian Customs ship Oceanic Viking in a bid to further fuel international outrage.

Canberra has said it will extend the Oceanic Viking's original 20-day mission to monitor and photograph the Japanese whaling fleet in Antarctic waters claimed by Australia.

It's published photographs will also be used as evidence in court action launched against whaling company Kyodo Senpaku Kaisha by the Humane Society International, following an earlier Federal Court ruling that the company's operations in the Southern Ocean were illegal under Australian law.

"These photographs show the reality of the slaughter of these animals," Home Affairs Minister Bob Debus said. "They will help us to back up the Australian Government's argument in an international court case - the details of which are still to be worked out - that whaling should be stopped."

Last night the director general of the Institute of Cetacean Research, Minoru Morimoto, claimed the two whales photographed were not related.

He said the release of the photographs was part of an "emotional propaganda" campaign.

"They are not a mother and her calf as claimed by the media. It is important the Australian public is not misled into believing false information."

Morimoto said the smaller of the two whales was just over 5m in length, while the larger was just over 8m. They were both female, neither was "lactating", and their difference in size showed only "random sampling" in practice.

"It is necessary to conduct random sampling of the Antarctic minke population to obtain accurate statistical data," he said.

The Labor Government of Prime Minister Kevin Rudd has made the strength of its opposition to whaling clear to Japan, with the dispatch of the Oceanic Viking backed by representations by Foreign Minister Stephen Smith in Tokyo last week.

"We don't believe that the so-called scientific research is scientific research," he said after meeting Japanese Prime Minister Yasuo Fukuda and Foreign Minister Masahiko Komura.