The pipistrelle is the UK's most common bat

The two-year study by the Bat Conservation Trust and the RSPB, the first of its kind, was published on Wednesday.

In the UK, it is against the law to disturb bats or the places where they roost.

The report says two-thirds of "crimes" are by builders and calls for more developers to carry out conservation surveys before renovation.

Using a network of bat groups nationwide, the study identified 144 offences committed during the period and claims the actual figure is much higher

Bat crime is rife in the UK and the major perpetrators are developers Amy Coyte Bat Conservation Trust

Other perpetrators were households or churches destroying roosts without consulting specialists first.

There are 16 bat species left in the UK but six are classed as endangered or rare and six others as vulnerable.

Amy Coyte, chief executive of the Bat Conservation Trust, said: "This report provides concrete evidence for the first time that bat crime is rife in the UK, and that the major perpetrators are developers.

"We are aware of the need for development but this must be done sustainably, taking bats into account before building work starts and ensuring that the appropriate legal procedure is followed."

Joan Childs, author of the report and RSPB investigations officer, told BBC News Online: "There is so much destruction of bats and their roosts that it must be having an effect on bat conservation.

Bat facts Bats can live for up to 30 years They are the only mammals that fly They rarely live in belfries but prefer somewhere quiet and draught-free They often choose modern houses as roost sites One fifth of the world's 4,500 different species of mammal are bats The UK's commonest bat, the pipistrelle, is only 4cm long and weighs about 5 grams - less than a 2p coin

"This seems to be a good reason for the decline of bat species.

"And we suspect this is just the tip of the iceberg and there's a lot more crime out there."

She said a disturbance could lead to adult females abandoning their young or aborting in pregnancy.

Her report says existing legislation needs strengthening in Northern Ireland and Scotland.

It also calls for better police training and resources to prosecute offenders.

The RSPB said the owner of a company in Hampshire was fined �1,500 in 2001 for damaging the resting place of pipistrelle bats when removing asbestos from a site prior to development.

In 1991, the greater mouse-eared bat became extinct in the UK, although there was one sighting 11 years later.

It is estimated the most common bat in the country, the pipistrelle, which is seen at dusk, has declined by 30% in the last 30 years.