PEOPLE on Teesside were last night warned about being tricked into revealing bank account details over the telephone to fraudsters masquerading as debit card security firms.

Criminal tricksters are ringing people up, claiming to represent the security and fraud departments of Mastercard and Visa.

After quoting a fictitious company badge number, they tell the targeted victim their card has been flagged up for an unusual purchase pattern.

They are then asked if they have recently bought a device for blocking out cold calls for £249.99.

When the answer comes back 'no', the caller then asks to "verify'' the person's credit card details, including the important PIN number, before ringing off.

Two cases of telephone fraud have so far been reported to Middlesbrough Council, only after the victims double-checked with the genuine card security divisions to find they had been conned.

Their experience has prompted both the local authority and Cleveland Police to alert residents to be on their guard.

Councillor Barry Coppinger, the council's executive member for community safety, said: "This is a very sneaky fraud, one in which the con artist does everything to build up a picture that they are genuine and put people at their ease.

"They ask very few questions and get you to volunteer information instead. But, of course, they ask the one question that matters, to get the information no one should divulge over the phone, their PIN number.

"Treat a phone call the same as you would a knock on the door and don't give out personal financial details."

Principal trading standards officer Jim McCluskey said: "Companies such as Visa know all the information on your card, as they have issued it - there is no need for them to ask for it again.

"If you give someone your PIN number, they can run up a string of purchases, so you always need to keep it safe and confidential.

"This is a clever con trick - a variation on an old theme - and people should always be on their guard when asked for personal financial details."

A spokeswoman for Cleveland Police said: "We would urge people not to give personal information to anyone over the telephone."