Newsweek's cover for its investigation into the life of Somaly Mam. Newsweek

A Newsweek cover story that exposed falsehoods in prominent anti-trafficking activist Somaly Mam’s story has prompted the New York Times' watchdog to ask one its most popular columnists, Nicholas Kristof, to audit his work on sex trafficking in Cambodia.

The Newsweek piece, published in May, brings to light several startling inconsistencies in Mam’s life story, and asserts that she lied about being sold into sex slavery. Among other unseemly things, the Newsweek investigation found that Mam, who became a charming fixture on the Western fundraising circuit and generated millions of dollars for her Somaly Mam Foundation, coerced several young women to lie about being trafficked.

Mam resigned from her post at the Somaly Mam Foundation shortly after the story broke. A statement from the organization on May 28 said Mam’s resignation was the result of an independent legal investigation into the allegations made by Newsweek.

On Monday, New York Times Public Editor Margaret Sullivan published a post calling on Kristof to revisit articles in which he portrayed Mam in a positive light and advocated for her foundation.

Kristof has dedicated several posts over the years to Mam’s work in Cambodia. In 2011, he referred to Mam as one of his “heroes” and wrote that it is “leaders like Somaly” who will help end human trafficking.

In a 2009 column, Kristof wrote about a young woman named Long Pross whom Mam had purportedly rescued from sexual slavery. Pross said that after being kidnapped and sold to a brothel, she was beaten and even had her eye gouged out by an angry pimp.

The girl with the scarred face appeared on Oprah and in the PBS documentary “Half the Sky.” But it turned out that her scars were not the result of abuse, but rather a surgery when she was 13 to remove a nonmalignant tumor covering her right eye.

Another of Mam’s girls confessed last year that she was never a victim of sex trafficking and that her story of being abducted was made up. She even said that Mam helped her rehearse her dramatic tale for the cameras.

Kristof responded to Sullivan’s with a post on Monday in which he expresses confusion over the allegations against Mam.

“I don’t know quite what to think,” Kristof wrote. “Somaly stands by her story, but she also resigned, which gives credence to the allegations.”

Kristof also wrote that while Somaly had no “license to exaggerate or fabricate” her story, he doesn’t think the controversy over her background should distract attention from the issue of human trafficking in Cambodia.

“One risk … is that the debate about Somaly’s back story will overtake the imperative of ending the trafficking of young teenagers into brothels,” he wrote. “Let’s remember that this is about more than one woman.”