The week-long Cibeles show in Madrid, which started yesterday, bans models with a body mass index (BMI) of less than 18, believing them to set an unhealthy ideal for teenage girls. The three models rejected by the organisers had a BMI of less than 16.

“A BMI of 16 is extremely low,” said Susana Monereo, a nutritionist and endocrinologist who weighed the 70 models due to appear at the show. Organisers refused to name the models, and said that they were not necessarily in danger. “Their health might be OK, but their appearance is extremely thin,” Dr Monereo said.

She said initially that the three rejected models were all British. But organisers backtracked quickly, saying the doctor had mistakenly assumed that the models were British after hearing them speak in English. A spokeswoman said: “In fact, they were of Italian, French and Polish nationality.”

The fashion show barred models it deemed to be excessively skinny from its catwalks in September 2006. The move, which was copied in Milan and elsewhere, was triggered by concerns for models’ health, and that anorexia was being encouraged among teenagers. Several models died from starvation in 2006 in Brazil and Uruguay.

The London Fashion Show has not followed Madrid’s lead. Many in the British fashion industry fear that top models might go elsewhere if they are forced to step on to the scales or to fatten up for the catwalk. The British Fashion Council made a series of recommendations last September, including a ban on using girls under 16 years of age. Models will also be required to present a medical certificate of good health from September next year.

The World Health Organisation defines a BMI below 18.5 as underweight. Spain has taken the lead on the so-called “size 0” debate, even asking high street shops to stop using unrealistically thin dummies.