Rimmel has secretly been holding castings for young girls to find a replacement for Kate, who turned 33 this month.

A source said: "Age catches up with everyone—even Kate. But she hasn't been told anything by Rimmel.

"At 33 she's getting on in terms of modelling. And she recently moaned about her face, saying she needed Botox.

"Rimmel is a range for the younger market so that worried them. Now bosses are looking for younger models who can give the brand a fresh approach. Girls have been contacted in secret."

The mum-of-one became the face of Rimmel in 2001. They considered ditching her four years later when it was revealed she was a cocaine addict. But she was kept on and secured more deals with other companies to take her earnings last year to £30 million.

Kate, who is dating Pete Doherty, is now in talks with posh cosmetics firms to launch her own make-up range.

She admitted recently she needed to take action if she wanted to carry on as a model. She said: "I need to think about getting Botox done soon, probably later this year. I can't be wrinkly.

"A few people at the agency have commented on it and no matter how much you try to ignore it, you can't.

"I don't think there's anything wrong with having a bit of work done— as long as my face isn't frozen."

Last night Rimmel refused to comment.