Nude photos of the Mamma Mia! star with an ex-boyfriend have appeared on Celeb Jihad and the star's legal team has demanded they are taken down immediately.

They insist the private images were illegally obtained by a third party and leaked to the site without Amanda's consent, according to TMZ.

Her lawyers have also asked the website bosses to preserve any evidence related to the leak, which is also linked to pictures of Emma Watson, whose lawyers have warned website owners not to publish the stolen personal photographs from a fitting with a stylist.

The pictures were reportedly hacked from the Harry Potter star's personal computer and posted online, prompting the 26-year-old's representative to assure fans none of the shots feature a naked Emma, despite reports to the contrary.

"Photos from a clothes fitting Emma had with a stylist a couple of years ago have been stolen," a spokesperson says. "They are not nude photographs. Lawyers have been instructed and we are not commenting further."

The Seyfried shots could not have dropped at a worse time for the actress, who is preparing to become a first-time mum.

She became engaged to fiance Thomas Sadoski in September (16), and the couple announced the baby news in November (16) when Amanda debuted her bump at a Givenchy red carpet event.

The scandal is unlikely to upset her actor fiance, who recently gushed about the mum-to-be in a TV interview.

"I spend a lot of my time looking at this bump that’s growing inside of her just thinking, looking and talking to that child and going, 'You have no idea how lucky you are to have a mum like this'," he told Harry Connick, Jr. "She’s incredible. I couldn’t be more proud of her for who she is as a mum already."

The couple is currently planning a low-key wedding.