Smallville stars Kristin Kreuk and Allison Mack have been implicated in cult that forced women to sleep with its leader and branded them.

The pair were members of Keith Raniere's group NXIVM (pronounced nexium), in which women were forced to sleep with Raniere and forcibly branded near their groins, the New York Post reports.

Raniere was arrested in Mexico on March 25 and it has been reported Mack, as part of the cult's leadership, can expect to be arrested soon too.

Smallville gave both actresses their big break during its run from 2001 to 2011. Kreuk played love interest Laura Lang while Mack played best friend and journalist Chloe Sullivan.

Kreuk was the first to join NXIVM around 2005/2006 and she brought Mack into the cult shortly afterward.

"Allison was used, as was Kristen, as a lure to bring in other women because of their celebrity status," Frank Parlarto, who broke the story of the cult in June 2017, told the New York Post.

In 2012 the Albany Times Union alleged Raniere was having sex with underage girls. Kreuk left the cult, but Mack stayed on.

According to Mr Parlarto, after Kreuk had left Mack was instrumental in coming up with the idea to brand the cult members, using a cauterising pen bearing a combination of her initials, AM, with Raniere's, KR.

"She started as a slave and she became a slave master," Mr Parlato claimed.

"Her nickname among defectors is 'Pimp Mack'."

Newshub.