Teachers in France have accused their government of using the tactics of dictators by enacting a law that imposes an "official history" of their country, requiring them to highlight the "positive aspects" of the French empire.

They claim the legislation ignores the torture, slavery and massacres "that sometimes went as far as genocide" and sometimes accompanied French colonialism.

The law aims to protect the reputations of "pieds noirs" - French people born in Algeria - and "harkis", Algerians loyal to France who were allowed to settle in the country when Algeria became independent in 1962. The legislation states: "School programmes are to recognise in particular the positive role of the French presence overseas, especially in North Africa, and give an eminent place to the history and sacrifices of fighters for the French army raised in these territories."

Hubert Tisson, general secretary of the History and Geography Professors' Association, said: "History shouldn't be used as an instrument to benefit this or that group or community.

"It's for historians to write history and for teachers to teach it. There shouldn't be an official history as in dictatorships."