London: Families have been handed a new weapon to block unwanted phone calls.

BT has launched the BT6500 telephone which, the company claims, will stop the menace of silent calls, withheld numbers, and overseas marketing scams.

Users can also programme specific numbers that they want blocked. Rogue firms, many of them based in India, are responsible for a very large proportion of the nuisance calls to consumers.

They target individuals with bogus promises of refunds on the mis-selling of payment protection insurance or compensation for accidents. The aim is to create a lucrative list of names and contact details that can be sold on to claims management companies who then take up the cases and charge huge fees.

The BT6500 will give users the power to block up to 80 per cent of unwanted calls, according to the company.

Frustrated customers are making more than 50,000 calls to its Nuisance Calls Advice Line each month. At the same time the telecoms regulator, Ofcom, has revealed it is getting around 3,400 complaints a month about silent calls, which are particularly disturbing. These are caused by call centre computers which automatically dial thousands of numbers at once.

Of those who receive silent calls, 57 per cent receive five or more a month, causing annoyance and, in many cases, distress and anxiety.

Ofcom has revealed that just over seven in ten people have received live marketing calls on their fixed-line phone in the past six months. Older people are more likely to have been affected, with four in five aged 65-74 receiving these types of calls.