British actress Anna Friel has become the latest star to face criticism over her promotion of a controversial liquid diet which she uses to maintain her youthful looks.

The Pushing Daisies star, 36, has admitted using the Master Cleanse over a period of two months, cutting out solid food and surviving on a drink of maple syrup, cayenne pepper, lemon juice and water.

Friel told Britain's Grazia magazine she also uses the diet to improve her skin, saying, "I've been drinking it for two months and I feel so much better and my skin has really benefited. If you're vain, as you get older you start thinking, 'I've got to do everything I can to save my skin'. I've tried everything."

However, Friel's comments have sparked a backlash among critics, who fear the actress is setting a bad example to impressionable young girls.

Sioned Quirke, of the British Dietetic Association, tells Britain's Daily Mail, "(The diet is) extreme and unnecessary... From a nutritional point of view, you are lacking in all the essential nutrients which your body requires on a daily basis to function.

"How could you possibly feel better if you are depriving yourself of everything that your body needs to survive? If you are lacking in these nutrients for a matter of days, let alone weeks, your body will suffer. It's a myth that what you eat affects your skin. We have a liver and it's very good at its job. So any detoxing that needs to be done is done by the liver...

"I can't imagine anyone surviving on it for longer than a week, let alone two months, so you've got to take what she (Friel) says with a pinch of salt (don't take it seriously)."

The diet has been used by stars including Demi Moore, Beyonce, and Gwyneth Paltrow, and has previously drawn criticism over its extreme measures to aid weight loss.