Representatives for Pacific Rim star Charlie Hunnam have denied reports that the up-and-coming British actor is set to star as kinky billionaire Christian Grey in the adaptation of "mommy porn" literary sensation Fifty Shades of Grey.

Variety reports that while Hunnam is on a list of possible contenders for Sam Taylor-Johnson's film, no final casting decision has been made. The studio, Universal, is said to be prepared to take its time over the process. Fifty Shades of Grey is due to debut in cinemas next August.

The story tells how Grey recruits a young virgin, Anastasia Steele, to be his sex slave. EL James's infamous knee-trembler trilogy has sold more than 70m copies worldwide, and there has been furious speculation over who might play the business magnate and his lover. So far, no casting details have been revealed.

Hunnam, who made his name in the cult US TV show Sons of Anarchy (and long prior to that, the British children's series Byker Grove), is riding high after strong reviews and decent box office returns for Guillermo Del Toro's Pacific Rim. The sci-fi action movie has made headlines for achieving a likely sequel via an impressive $100m box office return in China, even though its tally of $98m in the US was considered something of a dud.

More on the Fifty Shades of Grey film

• Fifty Shades of Grey: Sam Taylor-Johnson confirmed to direct