Waving a broomstick above his head, Maxime leaps up and down on a pavement in Central Paris. Is he mad, passers-by wonder, or drunk? No, his comrades explain, he is seeking to cut the global demand for energy.

Meet Le Clan du Néon, an increasingly popular environmental movement that wants to make the City of Lights a little darker. One tactic is to turn off neon shop signs at night by reaching the external fire switches that control them, usually found two or three metres up the façade.

“The signs are a waste of electricity and a visual pollution,” said Michael, a 27-year-old engineer, as Maxime used the broom to flick a switch above Aigle Azur, a travel agency, and plunge the shopfront into darkness.

“It’s crazy that when we all need to save energy, these neon signs are left on for 24 hours day,” he added.

Le Clan was set up in Paris, but its light-hearted and low-tech activist approach to ecology has been a hit across the country with students, many of whom see the antineon activity as a nocturnal lark. Groups have sprung up in Normandy, Bordeaux, the Alps and Dordogne. Members from the latter have posted an internet video that says that in a region bereft of night life, turning out the high street lighting is as good a way of passing the time as any.

“It’s true a lot of people do it for fun,” Michael said, “but at the same time, it’s important.”

The thousands of shop signs left on at night in Europe consume tens of gigawatt hours of electricity a year. In France, where the nuclear industry supplies 80 per cent of electricity, the result is more radioactive waste. Elsewhere, it is hundreds of tonnes of CO2 emissions. “If all the neon signs in the world were turned off, the impact on global warming would be very significant,” said Nicolas, 28, another Le Clan member. “There ought to be a law against it, but since there isn’t, we have to go around doing it ourselves.”

The evening action started at 11pm in Place de la République, where Michael shimmied up a drainpipe to turn off the red sign of Nouvelles Frontières, another travel agent. Nicolas then climbed on Maxime’s back to switch off the 26 neon tubes of Salon Régence, which organises wedding receptions. Then the lights went out at Société Générale and BNP Paribas, the French banks.

“This is fun,” said a middle-aged man who stopped to watch. “Can we come with you?”

“But is it legal?” asked his wife. “I can’t imagine the shopkeepers are going to be very happy.” Le Clan assured her it was and Maxime, 27, ran across the road and stretched the broom up to switch off an hotel sign.

Not everyone was smiling. The owner of Le Dogon, a restaurant, stormed out to berate the group. “How are tourists going to find the hotel now?” he demanded. “You can’t do anything in this country any more because of all these people with a cause to defend.”

Times Recommends

• Should Knox’s trial even have reached the courtroom?
• 'Was it real?' The US bailout nightmare
• Iranian opposition plays the long game