Dame Helen Mirren has a "filthy" sense of humour.

The 64-year-old actress stunned her 'National Treasure: Book of Secrets' co-star Justin Bartha with her saucy quips and crude remarks when they worked together, but he admits he found her confidence "sexy".

Justin - whose next movie 'The Rebound' co-stars Catherine Zeta-Jones - said: "Helen is the only person I've ever worked with that I've had a crush on.

"She's so sexy, smart and talented and loves having fun but if I thought Catherine Zeta-Jones was bawdy, Helen was filthy.

"There was a scene where Nicolas Cage had to stick his hand in a crevasse and pull a lever and while he was doing it, she leaned over and said something so suggestive, all I could do was look at her in shock and say, 'Dame Helen!'.

"But she loves having fun and the fact she's so comfortable in her own skin is what makes her so attractive. "

Justin - who is in a relationship with actress-turned-designer Ashley Olsen - also spoke of how much he enjoyed working with Catherine on 'The Rebound' and loved spending time with her husband Michael Douglas and their children Dylan, nine, and seven-year-old Carys.

The 31-year-old star added in an interview with the Daily Mail newspaper: "Everything she does workwise is in order to get back home to her kids and her man.

"After we finished shooting, they invited me to their family home in Majorca. They have a wonderful life out there."