Justin Bieber was "a brat" on 'CSI' set

CSI star Marg Helgenberger has criticised Justin Bieber's behaviour during his two guest stints on the series, describing him as "a brat".

Helgenberger, who plays Catherine Willows on the CBS drama, made the comments during an interview on a French radio station this weekend, when asked how the cast had responded to the Canadian popstar's involvement.

"Justin Bieber wasn't bad," the actress said, according to TMZ. "He had never acted before."

However, when pressed, Helgenberger admitted that he had often acted childishly during working hours.

"I shouldn't be saying this, but he was kind of a brat [on the set]," she explained. "He was very nice to me, but he locked one of the producers in a closet, and he put his fist through a cake that was on the actors' table."

Bieber made two guest appearances on CSI as teenage bomb expert Jason McCann, before his character was dramatically killed off in February.

The final episode of the 11th season of CSI: Crime Scene Investigation is scheduled to air on May 12.