Offences involving bogus callers who prey on vulnerable or elderly people are on the increase, according to the latest figures.

Official statistics reveal that there are 12,000 such incidents recorded each year.

But a Home Office task force believes the real figure is almost 10 times higher - with victims too frightened or embarrassed to report the crimes.

The research - published by the British Gas Help the Aged Partnership - suggests bogus callers are part of a highly organised, professional criminal fraternity.

'Devastating' effects

They pretend to be trades people, from gas, electricity and water companies and even pose as police officers to gain entry into older people's homes.

They often travel long distances and exchange information through a network of associates.

Their mainly female victims have an average age of 78, and are targeted because they keep cash and valuables in the home and are least likely to be able to defend themselves.

The effect of such crimes can be devastating, with victims suffering heart attacks, strokes and worsening mental health.

Police say the tragedy of such crimes is that they are preventable through measures including a chain on the door and double checking a caller's identification.