The Emperor penguins which won the hearts of millions of children in the film Happy Feet have suffered a devastating population slump in the last 50 years, according to a report.

Many colonies have fallen in size by 50 per cent as the penguins have been squeezed by the effects of climate change and overfishing, the WWF said in its report, Antarctic Penguins and Climate Change.

The report is published today to conincide with its presentation to officials at the United Nations summit on climate change in Bali.

Emperor penguins are one of four species of penguin which breed on the Antarctic ice and are increasingly being driven from their traditional territories.

Chinstraps, gentoos and Adelie penguins join the emperors on the ice each breeding season but they are all finding themselves pushed into a smaller area.

Sea ice on the western peninsula of Antarctic has retreated 40 per cent in the last three decades and is thought to be partly to blame for huge falls in the stocks of krill, a shrimp-like creature eaten by the penguins. Another factor is overfishing by humans.

The quantities of krill, which live under the ice where they feed on microscopic plant life, are estimated to have fallen 80 per cent in the last decade alone in part of the conbtinent’s western peninsula.

Warming in the Antarctic western peninsula is taking place about five times faster than other parts of the planet.

Nesting sites are destroyed by the the melting ice and the emperor penguins have suffered more thyan any other species in Antarctica.

Gentoos and chinstraps are being forced further south by the warming temperatures and this is putting extra pressure on the emperors and Adelie species.

All four species are, the WWF said, suffering under climate change and will continue to do so even the greenhouse gas emissions driving global warming is halted because carbon dioxide has an effect on the climate that can last decades.

Emperor colonies at Point Geologie on the western peninusula in Antarctica have halved in number in the last half century while chinstraps in the region have seen populations fall by two-thirds because of food shortages.

Gentoo penguins are increasingly dependent on krill because other fish stocks have fallen in size after being caught by trawlers.

Adelie penguins on the peninsula have fallen in number by 65 per cent in the last 25 years.

Emily Lewis-Brown, of WWF, said: “As the ice melts, these icons of the Antarctic will have to face an extremely tough battle to survive.

“One of the coldest environments in the world is actually seeing some of the fastest rates of global warming, and unless action is taken to reduce global CO2 emissions, the future of many Antarctic species looks bleak.” She added: “The UN climate change summit underway in Bali must agree a process now which results in comprehensive, ambitious, and fair global emission reduction targets.

“It’s vital that government’s agree upon a clear, shared vision to keep global warming to less than 2°C above pre-industrial levels.”

There are 17 species of penguin, all native to the southern hemisphere.

Emperors are the biggest species and the males remain with the egg on the ice during winter. They can survive blizzards, months of hunger and temperatures down to -49C.