The publisher’s rebuttal follows claims, made in the Daily Mirror, that the new Harry Potter book was being printed “in eastern Germany amid Cold War-style secrecy” by Bertelsmann subsidiary GGP.

The Daily Mirror went on to assert that workers at GGP were being forced to work in total darkness, in order to prevent them from reading the book and revealing the ending.

Bloomsbury publicity director Katie Bond described the claims as “clearly false”, while a spokesman for GGP said that the firm was unable to release information about its clients and their orders.

Bond added that the publisher would not comment on the printing or distribution of the novel prior to publication, for security reasons.

It is thought that Blooms­bury has also remained loyal to St Ives subsidiary Clays for production of the final instalment. The Suffolk-based division had printed the UK versions of all six previous Potter books.

Bloomsbury has used GGP in the past to print English-language versions for the German market.