The organisers of Madrid Fashion Week have announced that they are banning skinny women to develop a more healthy image for the event this month. If any very skinny models do turn up, they will be classed as unhealthy and in need of medical help.

The move has been heralded as good news for younger and lesser-known models, who often force themselves to become thin in the battle to secure a place among the top flight. But pear-shaped females should not celebrate too heartily, for the leading names of world fashion are showing no sign of following in the Spaniards’ footsteps. The Pasarela Cibeles trade fair in Madrid is a minnow compared with the big fish of Milan, Paris, New York and London fashion weeks.

Madrid city council, which sponsors the fashion week, has ordered that every model on show must have a body mass index (BMI) of at least 18. Models who are 5ft 9in (1.75m) tall must weigh a minimum of 8st 11oz (56 kg).

Esther Cañadas, Spain’s best-known model, does not qualify under the new rules as she is said to have a BMI of only 14. Almost a third of the women lined up appear to have been barred. The council promised that a nutritional expert would be on hand to check every model taking part in the shows, and that any woman found to have a BMI of below 16 would receive medical treatment.

The ban comes amid a row in Spain about the trend for extreme thinness on the catwalks and in high street shop windows. Cuca Solana, the organiser of the Pasarela Cibeles, was hauled before the country’s parliamentary commission for youth in April to defend the event against criticism that it pressures young women into losing weight.

According to the World Health Organisation, a woman is underweight if her BMI is less than 18.5, but Jesús del Pozo, vice-president of the Spanish Association of Fashion Designers, said that up to 40 per cent of the models who took part in last year’s event would have fallen foul of the new rules.

The organisers of London Fashion Week, which begins on September 18, said that they would not be introducing a similar rule. According to the leading agency Models 1, the models with the biggest pulling power are likely to be those with the smallest waistlines. “We have changed a lot in that there have been many more requests for bigger models, but on the catwalk long dresses do look lovely on tall, thin girls,” the agency said. “Girls who model at 15 or 16 tend to be thin girls, whose mums are thin, it’s part of their genetics, and obviously they look great in clothes.”

However, Lisa Armstrong, the Times fashion editor, asked: “Why do casting agents persist in using 15 and 16-year-olds to sell clothes to women in their thirties and upwards?” She added that the Madrid rules might have positive consequences for young British unknowns: “Madrid is a small fashion week and so this move will make very little difference to the bigger names, but younger and more inexperienced British models are sometimes sent to the smaller shows, effectively to practise.”

Sarah Doukas, Kate Moss’s agent, said that her agency, Storm, did not employ unhealthily thin women. “It’s useless to talk about body mass indexes. Who knows what that means apart from your doctor? It depends on different body types. Some people have different muscle density. I believe that girls should just eat healthily, exercise and just be normal. We just wouldn’t use someone who was really underweight or too thin.”

UNDERWEIGHT, NORMAL OR OBESE?

Times Recommends

• Gloves off as McCain lands Obama 'lie' jibe
• Anger as terrorist gets bail for IVF
• US hands palace of Saddam back to Iraqis