Caroline Flack began dating the pop star after meeting him as a contestant on Britain's The X Factor when she was 30 and he was just 17, and she was expected to tell all about the romance in a new book called Head Over Heels.

The book was also said to detail a rumoured fling with British royal Prince Harry, as her publishers Simon and Schuster announced, "Caroline will lift the lid on her personal life and relationships, including dating two of the world's most eligible bachelors, Harry Styles and Prince Harry."

However, Britain's Daily Telegraph newspaper now reports Flack has pulled the plug on the $160,000 (£100,000) deal because she was unhappy with the promise to detail her romances.

The book had been due for release in October (15).