Heavy price-cutting by supermarket rivals on the latest Harry Potter book has been blamed blamed for poor recent sales at bookshop chain Ottakar's.

The retailer sold the sixth instalment in the adventures of the child wizard for £11.99 at its 136 stores, but proved unable to compete with Tescos, Sainsbury's and Asda.

One of Ottaker's rivals sold the title for £4.99.

With trading conditions also difficult, Ottakar's said like-for-like sales in the four weeks to last Saturday showed a 6.7 per cent fall on a year earlier.

That left comparable business 0.3 per cent lower across a wider period covering the past 24 weeks - a performance described by the company as below expectations.

The company, which has six stores in the Midlands, said: "Recent sales performance can be attributed to a number of factors, including lower than anticipated sales of the latest Harry Potter book as a result of heavy discounting by supermarkets and other competitors."

An estimated two million copies of Harry Potter And The Half- Blood Prince were sold within 24 hours of its launch, including 400,000 at Tesco.

The current difficulties at Ottakar's are likely to have been compounded by the reluctance of publishers to release any other titles during the Harry Potter launch period.

All but one of the chain's stores staged events to promote the new Harry Potter book, which it hopes will attract young shoppers in the future.

The company added that it was still too early to predict the outcome for its full financial year, which is dependent on the Christmas trading period.

However, Teather & Greenwood analyst Sanjay Vidyarthi reduced his estimate for full-year profits to £8.2 million, from £7 million a year earlier.

He said: "While the likes of Tesco and Asda can afford the slimmest of margins on the top ten or 20 best-sellers, it must be remembered that 80 per cent of Ottakar's sales are from the back catalogue and it is unlikely that the supermarkets will ever encroach on this territory."

He pointed out the publishing schedule was set to improve in the second half, with strong titles in the sports and children's categories.