Harry Potter author JK Rowling has been named in a lawsuit which accuses her of stealing ideas for one of her best sellers from another British children's author.

An action raised in the High Court of England has named her as a defendent in a breach of copyright case against Bloomsbury Publishing, raised by the estate of writer Adrian Jacobs.

Ms Rowling said on Thursday she was "saddened" by the claims, which were "without merit".

Australian representatives for the late children's author say ideas from his 1987 book, 'The Adventures of Willy the Wizard - No 1 Livid Land', were stolen and used in 'Harry Potter and the Goblet of Fire'.

In 'The Adventures of Willy The Wizard', Mr Jacobs wrote of a dual world inhabited partly by wizards, with their own colleges, hospitals, transport and prisons.

The High Court Writ also claims the book talks of a year of wizard contests, similar to 'The Triwizard Tournament' which appears in the famous Potter tome.

Adrian Jacobs' literary agent was Christopher Little, the agent who famously discovered J.K.Rowling and now manages the multi-billion dollar international Harry Potter brand.

The Trustee of The Estate of Adrian Jacobs, Paul Allen, said: "The Estate- which acts independently of Adrian Jacobs family- has been in correspondence with lawyers for Rowling and her publishers for several years but have been repeatedly rebuffed.

"We have taken expert legal advice and we believe we have very strong case."

He added: "This court case is about upholding our legal copyright and seeking proper compensation to the Estate from J.K.Rowling and her Bloomsbury PLC her publishers for their substantial and sustained breach of our copyright.

"Adrian Jacobs was an original and visionary writer and his work deserves recognition"

The lawsuit against Bloomsbury was lodged in 2009, but Ms Rowling has only now been named in the case. Mr Allen said the Edinburgh author was added to the case after he learned that the statute of limitations to sue her had not run out, as previously believed.

Speaking on Thursday, she said:  “I am saddened that yet another claim has been made that I have taken material from another source to write Harry.  The fact is I had never heard of the author or the book before the first accusation by those connected to the author’s estate in 2004. I have certainly never read the book.

"The claims that are made are not only unfounded but absurd and I am disappointed that I, and my UK publisher Bloomsbury, are put in a position to have to defend ourselves. We will be applying to the Court immediately for a ruling that the claim is without merit and should therefore be dismissed without delay.”

His team say they are also examining whether copyright has been breached further in the making of the Harry Potter films, or in the creation of a theme park based on the books.

Rowling has not yet commented on the latest development, however, in June, Bloomsbury said the allegation that she had copied from Jacobs' work was "unfounded, unsubstantiated and untrue".