Still waiting for the next Harry Potter book? Don't hold your breath...

Millions of Harry Potter fans expecting the fifth book in the series this July are in for a disappointment – the next instalment, Harry Potter and the Order of the Phoenix, is unlikely to be published until next year.

Associates of the novelist J K Rowling denied last night that she had writer's block. Rowling had released one Potter book a year, with publication each July, from 1997 to 2000. But with the first Harry Potter film last November and the author's marriage on Boxing Day, there was no book last year.

And with her publishers, Bloomsbury, still waiting for the manuscript of the fifth book, there is no possibility of it reaching the shelves by July, as each Potter release is preceded by a massive global publicity campaign. Even a release this year now looks highly unlikely.

There has been speculation that she might have suffered writer's block. An unnamed friend was also quoted as saying that Rowling may be thinking of having another child. But her spokesperson said the reason for the delay was that the author had been through a hugely busy time and was still writing the fifth book.

"There has never been a date or an agreement on when she would deliver the manuscript," he said. "It might not be until next year. She is writing and enjoying writing; but she has an incredibly busy life as you can imagine."

Sean Smith, the author of her unauthorised biography, said: "She has more money than she ever dreamt of and a happy private life. The propulsion to write has disappeared. Creativity comes out of adversity."

But a spokeswoman for Bloomsbury said: "She is happily writing ... and as soon as we have the completed manuscript we will announce a publication date.

"We are looking forward to it as much as Harry Potter fans.

"I've no idea if it's taking longer because the book will be longer – all her books are different. But we are very relaxed about it."

The publisher's website, however, says that "in a perfect world the date would be early autumn 2002". Bookshops around the country have already been inundated with calls from people eager to find out when they can get their hands on a copy.

Rowling has promised to write seven instalments in total, one for each year Harry spends at Hogwart's School.

Harry Potter will be present this summer, even if not in book form. The video and DVD of last year's film of Harry Potter and the Philosopher's Stone are released tomorrow, and are likely to be the biggest sellers the market has seen. Tens of thousands of fans have already bagged their copy, with the online retailer Amazon.co.uk taking a record 36,000 pre-orders.

HMV will hold a special store opening at midnight tonight to meet the phenomenal demand and Asda will also throw open the doors of 58 stores.