The legal battle over the publication of a Harry Potter encyclopaedia has been delayed until mid-April, the New York judge presiding over the case announced yesterday.

JK Rowling's clash with American publisher, RDR Books, will be held off until the judge rules on whether the reference book is a violation of her intellectual rights or the copyright on the novels held by Warner Brothers.

Rowling and Warner Brothers took out a temporary injunction against RDR Books in October 2007 to prevent the publication of The Harry Potter Lexicon, an A-Z guide to the Potter novels.

The guide's previous publication date of November 28, 2007, was blocked by the lawsuit.

In the court papers, Rowling wrote: "I am deeply troubled by the portrayal of my efforts to protect and preserve the copyrights I have been granted in the Harry Potter books."

She claimed that Steven Vander Ark, editor of the Lexicon fan site and encyclopaedia, had exploited her trust by attempting to publish the reference book.

She said: "If RDR's position is accepted, it will undoubtedly have a significant, negative impact on the freedoms enjoyed by genuine fans on the internet.

"Authors everywhere will be forced to protect their creations much more rigorously, which could mean denying well-meaning fans permission to pursue legitimate creative activities."

The Harry Potter Lexicon is based on the popular internet fan site of the same name, a resource Rowling herself reportedly used when writing the later novels.

The author is preparing to publish her own definitive encyclopaedia of all seven Harry Potter books, the profits of which will go to charity.