The world's most famous polar bear is to be banished from Berlin zoo because of lack of cash – the first ursine victim of the credit crunch.

Knut the polar bear, who now weighs 210kg, turns two on Friday. But Berlin zoo will not be holding a party for its famous inmate, who has lived there since birth, announcing plans for his imminent eviction instead.

"He should go sooner rather than later," Heiner Klös, the chief bear keeper, said. "Knut must finally find a new home." He is set to leave by early 2010.

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More than 21,000 Berliners have signed a petition demanding that Knut be allowed to remain. The bear's fans plan to rent a site opposite the zoo on Friday for a Knut birthday party. The city's tourist industry did not welcome the news of the bear's departure.

"Berlin is about to lose one of its best ambassadors," said Christian Tänzler, of the tourist board. "For our visitors from abroad it will mean the loss of one of the city's true mascots."

Conservative estimates put the revenue that Knut has earned at €10m (£8.5m). Millions of cuddly Knut toys and T-shirts bearing his image have been sold, a Hollywood film has been made about him and he has even featured on the cover of the magazine Vanity Fair.

Berlin zoo cited financial concerns as the chief reason for the decision. To keep Knut, the zoo would have to raise €9m to pay for roomier quarters for him and a future mate. The city is still bankrupt and the credit crunch has destroyed hopes of an early recovery.

"We cannot afford it in such times of economic strain," a Berlin zoo spokesman said. It emerged that Knut's legal owner is Neumünster zoo in northern Germany; its polar bear Lars fathered Knut in 2006. Peter Drü, the Neumünster director, said his zoo alone would decide on Knut's future.

Zoologists are also concerned for Knut's psychological welfare. He was hand-raised for 18 months and zoologists have argued that because Knut only had contact with humans, he has developed psychopathic tendencies; even if he found a mate, Knut would not have developed enough to be able to properly respond to her advances.

Bear experts have insisted that Knut should be found a new home with other polar bears as soon as possible. The most likely option is a zoo in Gelsenkirchen, which has a three-year-old female polar bear called Lara.