Justin Timberlake 'tortured' Jessica Biel

Justin Timberlake "tortured" Jessica Biel by agreeing to make a movie with his ex-girlfriend.

The 'SexyBack' star is currently filming 'Bad Teacher' with Cameron Diaz – who he dated for four years until 2007 – and friends believe it has contributed to the problems in his relationship, which is rumoured to have ended.

A source said: "He tortured Jess by taking this role. They were having huge arguments on the phone and Jessica would get territorial and upset."

However, insiders claim Jessica's attitude has driven Justin, 29, closer to his 37-year-old co-star and they are friendlier than ever.

The source added to Us Weekly magazine: "There's lots of laughing, making fun of each other, kidding around off camera. They're having a ball together."

Justin reportedly confided in his pals that he has "lost respect" for Jessica.

It was recently claimed that Justin and Jessica, 28, had decided to split because their three-year romance was going nowhere.

An insider said: "Justin truly thought he'd found the one in Jessica and she felt the same. But the relationship just didn't seem to go anywhere.

"They've both been working incredibly hard and will remain friendly - but there's no more romance.

"It was mutual and they agreed it was best to part ways if things weren't going to head towards marriage and kids. They are both incredibly busy."

It was alleged today that Cameron is dating baseball star Alex Rodriguez. The two fell for each other after meeting at a Creative Artists Agency Super Bowl party in February.