Scientific advisors for the International Whaling Commission are calling for urgent changes to the way it issues whaling permits to Japan.

The group of leading scientists say Japan's scientific whaling programme isn't neccessary, and may not even be scientific.

Members of the International Whaling Commission's scientific committee have signed a letter published in today's Nature's journal.

In it, they've called for an urgent review of the way the commission assesses the scientific validity of Japanese whaling.

Japanese whalers have returned to the Southern Ocean where they intend to kill 333 minke whales this season.

Auckland University marine expert Rochelle Constantine said the killings don't provide useful findings.

"There are questions we can answer only using dead whales but none of those questions are really required to manage recovering populations."

Constantine said Japan's lethal research hasn't been as successful as non-lethal research.

"Recently at Raoul Island we put research tags into whales and took small tissue biopsy samples and those whales are swimming around Antarctica now."