French MPs have approved a law to ban the use of fashion models deemed to be excessively thin.

Under the law, models will have to show they have a Body Mass Index (BMI) above a certain level.

Modelling agents that break the rules face fines and six months in jail.

The lower house of parliament also passed a separate measure making it illegal to condone anorexia, a move targeting internet sites that encourage dangerous weight loss.

Up to an estimated 40,000 people suffer from anorexia in France, nine out of 10 of them women and girls.

The new law on fashion models, part of a wider Health Bill, won a majority vote in the National Assembly lower house of parliament on Friday and must now be approved by the Senate.

“Anyone whose body mass index… is below a certain level will not be able to work as a catwalk model,” it said.

The move would allow agencies to be “severely punished” if they forced models to undergo excessive weight loss, endangering their health, Olivier Veran, the Socialist MP who proposed the bill, told French news channel BFMTV.

He has said there would be regular checks to enforce the rule.

The deputy previously said models would have to present a medical certificate showing a BMI – the ratio of height to weight – of at least 18 before being hired for a job.

The average BMI for a woman in France is said to be 23.2.

Doctors say a normal BMI for adults is between 18.5 and 24.9, but some critics say the measure is not the best way of judging a healthy weight.

The National Union of Modelling Agencies has complained the ban would affect the competitiveness of French modelling.

But doctors and women’s rights groups have long campaigned against the image they say is too often put out by the fashion industry of young women of an unnatural and unhealthy thinness.