Eric Schmidt, Google’s executive chairman, has described China as the most “sophisticated and prolific” hacker of foreign companies in his upcoming book, according to leaked extracts.

“The disparity between American and Chinese firms and their tactics will put both the government and the companies of the United States at a distinct disadvantage," Mr Schmidt wrote, according to the Wall Street Journal. He argues that the Chinese state backed cyber crime for economic and political gain, making it the biggest online menace in the world.