As well as retreating, the vital front between cold sea ice and warmer sea water which causes an upwelling of nutrients supporting the krill on which the whales feed will also contract, reducing the amount of food available.

"Essentially, what we are seeing is that ice-associated whales such as the Antarctic minke whale will face dramatic changes to their habitat over little more than the lifespan of an individual whale," said WWF officer Heather Sohl.

The longer migration paths will not only increase the energy the whales use to get to their feeding grounds but also reduce the duration of the feeding season because of the time taken to get there, the report said.

The report is timed to coincide with the 60th annual meeting of the International Whaling Commission in Santiago, Chile next week at which Brazil will proposed the adoption of a South Atlantic Whale Sanctuary.

Whaling nations Japan and Norway are also waging a determined campaign to get the IWC's 1982 moratorium on commercial whaling lifted.

Especially at risk from the retreating Antarctic sea ice are the Blue Whale, the world's largest living creature, and the Humpback Whale.

These are only now starting to stage a comeback after being hunted to the brink of extinction in the 20th century before the IWC whaling moratorium came into force. Scientists predict that global average temperatures will rise by between 1.8 and 4.0 degrees Celsius this century due to burning fossil fuels for power and transport -- with faster and greater warming at the poles.

The WWF predictions are is based the assumption that average temperatures will rise by 2.0 degrees Celsius by 2042. (editing by Philippa Fletcher)