France's government is likely to back a bill banning excessively thin fashion models, a measure criticised by model agencies but supported by the public.

If passed, the bill plans to fine a modelling agency or fashion house that would hire these models and send the agents to jail, the health minister said on Monday.

Style-conscious France, with its fashion and luxury industries worth tens of billions of euros, would join Italy, Spain and Israel which all adopted laws against too-thin models on catwalks or in advertising campaigns in early 2013.

"We notice that the average weight of models in France is lower day after day, in France and elsewhere in many foreign countries. And often the models are subject to considerable pressure from the agencies and designers to lose more and more weight. You just need to see the images in the last fashion shows," Socialist lawmaker Olivier Veran, who wrote the amendments, told Reuters Television.

Models would have to present a medical certificate showing a Body Mass Index (BMI) of at least 18, about 55 kg for a height of 5'7", before being hired for a job and for a few weeks afterwards, he said.

"In the bill, I suggest that from now on, a model must go through a medical visit before she is hired which would evaluate the Body Mass Index (BMI) which is calculated by dividing the weight over the height square and this index is used by the World Health Organization to determine if someone is undernourished or even in a state of famine and I suggest that the medical certificate for work ability can not be delivered to people who are undernourished and who therefore are putting their life and health in danger," Veran said.

The law would enforce regular weight checks and fines of up to €75,000 (£54,000, $79,000) for any breaches, with up to six months in jail for staff involved.

But Sylvie Fabregon, the director of a model agency specialised in plus-size models, said the problem was not about catwalk models, who are naturally thin, but in retouched photos shown in magazines.

"Girls will have more complexes when looking at magazines. In magazines, all pictures are retouched. It would be better to tell young girls 'Be careful, magazines are not real life,'" she said.

The bill's amendments also propose penalties for anything made public that could be seen as encouraging extreme thinness, notably pro-anorexia websites that glorify unhealthy lifestyles.

In 2007, Isabelle Caro, an anorexic 28-year-old former French fashion model, died after posing for a photographic campaign to raise awareness about the illness.

Some 30-40,000 people in France suffer from anorexia, most of them teenagers.