The official Spanish translation is not due out yet

Translation mistakes and poor graphics litter the version of the book, issued five months in advance of the official Spanish volume's release.

But the author apologises for his or her shortcomings in notes in the book.

On one page the translator warns: "Here comes something that I'm unable to translate, sorry."

Readers will also find the translator admitting not knowing how to translate the word "breathy", while on another page, it reads: "You gave him 'the old one-two' (I'm sorry, I didn't understand what that meant)."

The cover is an exact copy of the English-language version, which has been on sale since 21 June. The book is 777 pages long, compared to the 870-page original.

Daily newspaper El Universal reported that two people had been arrested last month and charged with producing the bootlegs.

Legal action

Bootleg translations of the latest Harry Potter book have appeared all around the world.

Fans not content with waiting for the official translation have taken matters into their own hands.

German fans of the books were threatened with legal action after translating the book online.

In Chile, two men were arrested for producing their own translated copies of the Potter book.

The president of the Chilean Book Chamber business group urged people not to buy the book, which was selling for about $15 (£9.30), saying it was not just a pirated copy but also "a bad translation".

And in France, English speakers impatient for the book's official release in December have bought the original version, making it the first English book to top the best-seller list.