The comic star - whose story is currently being made into an $80 million Hollywood film - is being sued by Norwich based freelance writer and artist John Savage.
Mr. Savage has issued proceedings in the High Court claiming `Flanimals` is based on his book `Captain Pottie`s Wildlife Encyclopaedia`.
In his court documents, Mr. Savage states `Flanimals` breaches the copyright in his book by being "broadly the same in content and character", and claims both books involve "a whimsical take on the animal kingdom through the use of drawings and text".
Mr. Savage said: "The next stage is the High Court will be sent a copy of the writ to Mr. Gervais` lawyers and they have two weeks to decide whether to defend or accede to my request."
A spokeswoman for Gervais denied the claims and revealed the dispute has been going on for some time.
She explained: "This story goes back several years, when John Savage first made contact with RickyGervais` representatives.
"At the time it was made clear the concept and illustrations of `Flanimals` pre-existed John Savage`s work.
"To date RickyGervais has not received any formal court proceedings from Mr. Savage."