The weather is looking decidedly blustery in Hundred Aker Wood. Lawyers representing the family that owns the merchandising rights to Winnie the Pooh are stepping up their fight with Walt Disney, the entertainment group which has turned the English children's books into a huge multi-media franchise.

The Hollywood attorneys of New York literary agent Stephen Slesinger, which bought the rights from author AA Milne in 1929, have filed a suit to terminate Disney's licence and to claim damages for "hundreds of millions" of dollars.

The filing is an escalation of a decade-long battle between Mr Slesinger's family and Disney, which had previously focused on the payment of royalties. In what has become an acrimonious dispute, the Slesinger family has alleged that Disney has been withholding royalty cheques since 1983.

In an earlier trial, the Florida-based family claimed it was owed $35m (£24m) from video, DVD and software sales. Walt Disney rejected the claim, insisting that the products in question were not covered by its agreement with the firm, Stephen Slesinger. The judgement from that case has not yet been made public.

Bert Fields, a lawyer representing Stephen Slesinger, said: "We are seeking damages in the hundreds of millions and we feel very confident."

The attorneys for the heirs said that Winnie the Pooh is now more valuable to Disney than Mickey Mouse. They claim the character drives about $4.5bn of Disney's $25bn annual revenues.