France's lower house of parliament today adopted a groundbreaking bill that would make it illegal for anyone to publicly incite extreme thinness.

Fashion industry experts said that the law, which would apply to magazines, advertisers and websites, would be the strongest of its kind anywhere.

Valerie Boyer, from the ruling UMP party, proposed the new legislation which she said would give judges the power to imprison offenders and fine them up to 30,000 euros (£24,125) if convicted of "inciting others to deprive themselves of food" to an "excessive" degree.

The National Assembly approved the bill after the legislation won unanimous support from the ruling conservative UMP party. It will go to the Senate within a few weeks.

French lawmakers and fashion industry members signed a nonbinding charter last week, on promoting healthier body images. And, in 2007, Spain banned ultra-thin models from catwalks. But Boyer said such measures did not go far enough.

The bill reflects concerns about pro-anorexic (so-called pro-ana) websites, said to encourage extreme weight loss. But Boyer said the legislation's impact would be wide-ranging.

The bill is the latest in a series of measures to be proposed following the 2006 anorexia-linked death of a Brazilian model prompted efforts to tackle eating disorders within the fashion industry.

Didier Grumbach, president of the influential French Federation of Couture, said: "Never will we accept in our profession that a judge decides if a young girl is skinny or not skinny. That doesn't exist in the world, and it will certainly not exist in France."

Marleen S Williams, a psychology professor at Brigham Young University in Utah, who researches the media's effect on anorexic women, said it was almost impossible to prove that the media causes eating disorders.

She said studies showed fewer eating disorders in "cultures that value full-bodied women". But she added that she fears the new French law, if ratified by the Senate, would amount to "putting your finger in one hole in the dike, but there are other holes, and it's much more complex than that".

The French health ministry says the vast majority of the 30,000 - 40,000 people with anorexia in France are women.