Women should go “low carb” if they want to conceive - because doing so could increase the chance of success by five times, say fertility experts.

They say one portion a day is the limit for those trying to conceive, and advised cutting out all white bread, pasta and breakfast cereals.

Leading doctors said they are advising patients with fertility problems to radically change their diet, after evidence showed that high amounts of refined carbohydrates can seriously damage conception chances.

British clinics yesterday revealed that they have begun enrolling patients on nutrition courses and even cookery classes, amid concern that increasingly stodgy diets are fuelling fertility problems.

Dr Gillian Lockwood, executive director of fertility group IVI, said she advises all patients to cut their carbohydrate intake, amid a growing body of evidence linking such foods to impaired fertility.

High levels of carbohydrates - especially refined ones - are already known to affect the body’s metabolic functions, and can fuel obesity, which in itself reduces fertility.

But experts said there is growing evidence that a typical western diet, with high reliance on convenience foods, high in carbohydrates, badly affects a woman’s reproductive system, reducing the quality of her eggs.

Fertility experts advised all couples trying to conceive to look closely at their diets - and said there was strong evidence that women in particular should cut back on carbohydates.