Amazon says that e-book sales have overtaken those of print versions.

Two years after it introduced the Kindle e-reader, the company said yesterday that, so far in 2012, for every 100 hard and paperback books bought through the site, 114 had been purchased in electronic form.

This even includes books which have no Kindle version, Amazon said, but did not take into account editions which could be downloaded free of charge.

Unlike for its printed books, Amazon does not release independently checked figures for e-book sales, and a company spokesman refused to discuss the matter with the Guardian newspaper.

But in a statement, Jorrit van der Meulen, vice-president of Kindle EU, said: "Customers in the UK are now choosing Kindle books more often than print books, even as our print business continues to grow.

"We hit this milestone in the US less than four years after introducing Kindle, so to reach this landmark after just two years in the UK is remarkable."