Eleven of Britain's 16 bat species are now under threat

Officers are to be trained in how to investigate damage to roosts as part of Operation Bat, which is officially launched on Wednesday.

Police will also be warning builders, roofers and pest control workers that it is a crime to destroy bat roosts.

Conservationists hope the crackdown will help protect dwindling native numbers of the nocturnal mammal.

Bats are a very good indicator of well-being of our natural habitat Pc Geoff Culbertson

Of 16 species of bat in Britain, two are now endangered, six are vulnerable and three are rare.

The maximum fine for destroying a roost is �5,000 for each bat, which could be multiplied many times for a typical roost of about 20 pipistrelles, the most common British species.

Pc Geoff Culbertson, a wildlife crime officer from Hampshire Police who helped develop Operation Bat, told BBC News Online: "Bats are a very good indicator of well-being of our natural habitat.

"The Environment Agency use the presence of the daubenton bat - which skims the surface of lakes and rivers and picks off insects to eat - to tell if a river is in good condition.

"A lot of bat babies are born in June, so there will be maternity roosts all over the place, where mothers leave their babies while they go out and forage for food.

"It is vitally important that we take action to prevent bat roosts from being destroyed and one of the best ways of doing that is to raise awareness."

Extinct mammal

The Bat Conservation Trust and other conservation groups are among those backing the new tougher approach, which was prompted by Joint Nature Conservation Committee research showing bat numbers were under threat from law-breakers.

In the 19th Century, greater horseshoe bats lived in London's parks, while today they are found only in the rural south west and Wales.

Between 1978 and 1993 the population of pipistrelles slumped by about 70%, according to the National Bat Colony Survey.

And in 1991 the mouse-eared bat became the first mammal to become extinct in this country since the wolf, which disappeared 250 years earlier.