Shops and offices throughout France will be forced to turn off their lights overnight in a bid to fight light pollution, the country's environment ministry has announced.

Under the new law, which comes into effect on 1 July, lights in shop window displays will be turned off at 1am. Interior lights in offices and other non-residential buildings will have to be switched off an hour after the last employee leaves. Local councils will be able to make exceptions for Christmas and other special occasions, and in certain tourist or cultural areas.

The move, announced on Wednesday, is expected to save 250,000 tonnes of CO2 – enough energy to power 750,000 French households for a year.

The French ecology minister, Delphine Batho, said she hoped the law would change attitudes in France and help the country become a pioneer in reducing light pollution.