The Amazon Kindle 2's text-to-speech functionality is "legal", the etailing giant has insisted in a statement to the press.

The statement follows comment and criticism from the audio book industry on the feature, including from the American Author's Guild organisation, that suggested it trespassed on audio book rights.

Amazon said: "Kindle 2's experimental text-to-speech feature is legal: no copy is made, no derivative work is created, and no performance is being given".

Amazon, that bought audio book company Audible in January 2008, has compromised and says that book rightholders can decide on a title-by-title basis if they want text-to-speech disabled.

Amazon said of the decision: "We strongly believe many rightsholders will be more comfortable with the text-to-speech feature if they are in the driver's seat".