Anyone “provoking people to excessive thinness by encouraging prolonged dietary restrictions that could expose them to a danger of death or directly impair their health” could be punished, says the amendment.
The health ministry estimates that there are 30,000-40,000 anorexics in France and that 90 per cent of them are young women.
The new law is “necessary”, said the deputies who proposed the amendment, “because the authorities cannot do anything about those websites known as ‘pro-Ana’ ".
The law “will not call into question the idea of freedom of expression on the internet”, said Socialist MP and doctor Olivier Véran while moving the amendment.
The fashion industry is at the centre of the anorexia controversy.
Because of the ubiquity of slender models on catwalks, some - but not all - agencies have already taken steps to exclude unhealthily thin models from shows.
Véran proposed last week proposed another amendment banning ultra-thin catwalk models.
Although French authorities have agreed a voluntary charter with the industry last year, a parliamentary committee rejected the proposal with a number of MPs on both sides of the political divide arguing that it would amount to job discrimination.