Michael Lewis, author of 'Flash Boys', the controversial book on high-frequency trading, has accused regulators investigating HFT of paying lip-service to probes into the practice.

Flash Boys, which was released just over a year ago, provoked an intense reaction from the financial industry, with its allegations that HFT was rigging the US stock markets. It followed the story of Brad Katsuyama, a former Royal Bank of Canada trader, who set up dark pool IEX after learning about the practice.