POLICE and BT have warned of the dangers of taking mystery phone calls at face value.

They said a foreign company is offering a prize holiday that could end up costing the person receiving the call hundreds of pounds.

Those who answer the call are told they have won an all-expenses-paid exotic trip and are asked to press nine to hear more details.

They are then connected to a premium rate line which costs a reported £20 per minute. Even if people receiving the calls hang up, they will stay connected for a minimum of five minutes, costing £100.

Eventually, after further instructions, the recipients of the call receive a message to say they are not one of the lucky winners, but the bill for the call could be as high as £260. Another part of the call, which comes from abroad, asks for a postcode and house number to be keyed in, which could lead to future security problems.

As the calls are originating from outside Britain, phone companies are powerless to act.

Sgt Ian Coop, of Bolton Police, said: "People need to be aware of accepting telephone calls from cold callers and be mindful of the things they are telling you. The advice is: If you are not sure, hang up."

A BT spokesman said: "If anyone receives a call they are not sure about, then the advice would be to just replace the receiver. If something sounds too good to be true, it generally is.

"We are unable to stop anyone from ringing another person but the person who receives the call can put systems in place to block certains types of calls, for instance if you don't recognise the person's number or want to stop certain companies from cold-calling you."