Owners of over-sensitive security lights which activate in a stiff breeze could be fined up to £5,000 from next week.

New legislation will make it a criminal offence to annoy neighbours with artificial light.

Bradford Council dealt with 17 such complaints in the last 12 months, but the Clean Neighbourhoods and Environment Act comes into force on Thursday, April 6, giving inspectors more muscle to deal with the nuisance.

Kate Lett, Bradford Council's environmental health manager, said: "The legislation is likely to be used by small groups of individuals for a specific problem.

"It will be a small spanner in the toolbox we have as public environmental health officers, but there is a lot to learn as to what constitutes a statutory nuisance in terms of light."

Exemptions built into the legislation include lighting at airports, lighthouses and prisons, but she admitted sports stadia and other floodlit pitches could be reported: "There is always a defence - particularly for commercial premises - if they have taken steps as far as reasonably practical. They would have to show lighting has been designed in a way to minimise spill-over of light where it can cause a nuisance. John Baruch, a Bradford University astronomer and head of the robotic telescope team, said light pollution was a real problem for the district's sky-watchers.

He hopes the legislation will help: "On a normal night in Bradford you see about 20 stars when you should see 4,000.

"Bradford is particularly bad - we must be lighting up Mars! Why are we wasting so much power lighting up clouds?"

Street-lighting, long considered to be one of the main causes of light pollution, is not covered by the legislation.

But Allun Preece, principal engineer for Bradford's street lighting, said new technology was tackling the issue.

"We are trying to use curved tempered glass bowls that are shallower and minimise light escaping up above the horizontal," he said. "This means most of the light goes where it should do - on to the road - but there will always be some bounce-back into the sky."