Responding to years of lobbying by the film industry, the French government has legalised the use of mobile phone jamming devices in cinemas, theatres and concert halls, to prevent audiences being disturbed by ring tones and telephone conversations.

Sophisticated technology means people can be prevented from receiving and making mobile telephone calls within 30 metres of the device.

Only emergency calls will be able to override the block.

French film-makers have said the use of mobile phones in cinemas was resulting in a "disastrous" impact on ticket sales. The change in the law is part of the government's campaign to make cinemas more enticing.

Patrick Devedjian, the French industry minister, said: "It's the same for concerts. You know how it is when thugs let their phones ring during a concert."

He added: "But that's all over now."

Until now, the use of blocking devices has been punishable with a fine of €30,000 (£20,660) or a six-month prison sentence.

French media said the jammers made by the British-based company Starport, which cost about €440, might be ordered for use in public auditoriums.

The move was first debated in 2001. However, there was uncertainty over whether jammers could block telephone signals in cinemas and theatres without disrupting signals in the surrounding streets.

A total block on calls has upset those who want to be contactable if their babysitter or employer needs to speak to them urgently.

Previously, France's telecoms regulation authority has tried encouraging concert audiences to use the vibrate mode on their phones or to switch them off entirely, but with no apparent success.

The president of the National Federation of French Cinema, Jean Labbé, said that jamming devices would transform the experience of going to the cinema in France.

"This will permit people to watch the film, and only the film," he told French radio.

Prison officials and school governors are also campaigning to be allowed to install similar devices, and some restaurant owners are doing the same.