A mum has described the trauma her daughter is still suffering after she saw a man masturbating in his car outside a school in Cam.

"I'm lucky she wasn't raped last night," the mum said, who went to straight to the police after she heard what happened from her 16-year-old daughter as she came dashing through the door. 

According to the mum, at around 6pm on Thursday her daughter was walking past Cam Everlands Primary School on Birch Road having been out with friends when she saw a dark-coloured car parked with its headlights on full beam. 

As her daughter went past and took a glance through the window she saw a man with his genitals exposed, pleasuring himself.

"She panicked - she didn't stop to get a description or note down the number plate - and she ran off.

"The car drove off too - the guy obviously realised.

"She came dashing through the door and told me what happened and I rang 999.

"For half an hour she was just stamping her feet in the kitchen. She couldn't get the image out of her head.

"She didn't expect that, she was just leaving her mates. She wasn't expecting to see that on her way home.

"It's digusting. How can anyone do that?"

Police are now investigating - if you have any information that can help call 101 quoting incident number 381 quoting the date of Thursday, December 20.

"I hope they catch the dirty rascal," the mum added.