The diet reportedly followed by the Duchess of Cambridge's mother Carole Middleton has been labelled "confusing, rigid, and ineffective" by the British Dietetic Association (BDA).

Experts named the Dukan Diet the worst weight-loss plan out of their five worst celebrity diets to avoid this New Year, saying it has "absolutely no solid science behind it at all".

The Dukan Diet, which is a four-phase diet that kicks off with a protein-only week, was described by the BDA as "so confusing, very rigid, full of very French foods that most Brits would run a mile from like rabbit and offal, and even Dr Dukan himself warns of the associated problems like lack of energy, constipation and bad breath."

The other celebrity diet fails in the list were: The Alcorexia diet, The Blood Group diet, The Raw Food diet, and The Baby Food diet.