Knut the polar bear has turned from a cuddly cub into a publicity-addicted psycho, one of his keepers has claimed.

Markus Roebke said Berlin Zoo's celebrity animal was obsessed with the limelight and howled with rage when denied an audience.

"Knut must go and the sooner the better," he said, insisting that the bear should be sent to an animal park where he received less attention

"He is addicted to the whole show, the human adulation. It is not healthy.

"He actually cries out or whimpers if he sees that there is not a spectator outside his enclosure ready to ooh and aah at him.

"When the zoo had to shut because of black ice everywhere he howled until staff members stood before him and calmed him down."

Knut was rejected by his mother after he was born in December 2006, prompting some animal activists to say it would be better for him to die than to be weaned by man.

The zoo let him live however and he has become a major attraction, pulling in millions of dollars in revenue so far.

Now Knut is bigger, the crowds are larger - and, his keeper warns, his mental health is deteriorating

Mr Roebke added: "The trouble is that he identifies himself as a human and not as a polar bear.

"And as long as he is with us he will always think of Thomas Doerflein, the keeper who brought him up when he was a baby, as his father. Knut needs publicity and that must change.

"We are not allowed to have contact with him and have received letters that if we breach this order our jobs are on the line. He is too unpredictable to play with now."

Mr Roebke is not the only observer to question Knut's sanity. In January, a prominent animal conservationist branded him "an animal psychopath".