Jk Rowling is being sued for £500 million for plagiarism.

The estate of little-known British author Adrian Jacobs has claimed Rowling's fourth novel 'Harry Potter and the Goblet of Fire' was copied from Jacobs' 1987 book 'The Adventures Of Willy The Wizard No 1: Livid Land'.

Jacobs' died in 1997 without ever reading a 'Harry Potter' novel - the first title in the hit series was published the same year - but his son and grandson are convinced Rowling studied and duplicated his 36-page story, which also featured a child who discovers he has magical powers.

They claim Jacobs' sent his manuscript to Christopher Little, the literary agent at Bloomsbury Publishing who went on to represent Rowling, but it was rejected.

The estate is now suing Rowling and Bloomsbury Publishing for plagiarism, lodging legal proceedings at Britain's High Court.

Legal papers filed by Jacobs' estate list similarities between the books, including "shared references" to a wizard train and prison and a magical contest where the boy wizard must rescue human hostages taken captive by half-human creatures.

In addition to £500 million in damages, the estate is seeking an injunction to prevent further sales of the offending book, or a share in the tome's profits.

Rowling is estimated to have a personal fortune of £560million.

Bloomsbury Publishing has branded the allegations "unfounded, unsubstantiated and untrue".

A statement said: "JK Rowling had never heard of Adrian Jacobs nor seen, read or heard of his book 'Willy the Wizard' until this claim was first made in 2004 - almost seven years after the publication of the first book in the highly publicised 'Harry Potter' series.

"'Willy the Wizard' is a very insubstantial booklet running to 36 pages which had very limited distribution. The central character of 'Willy the Wizard' is not a young wizard and the book does not revolve around a wizard school. This claim is without merit and will be defended vigorously."