Frustrated residents have taken it upon themselves to warn potential victims that thieves are operating a cashpoint scam in Hampstead - after losing patience with police and the bank.

The South End Green Association has taped a beware sign to the ATM in Heath Hurst Road, which thieves have been tampering with.

The technique, known as “cash trapping”, blocks notes from being dispensed.

After puzzled cashpoint users walk away, thieves remove a thin strip of aluminium from the ATM and collect the cash.

Barclays Bank which owns the cashpoint, has declined to step up security measures around the trouble hotspot, but police say they are investigating the problem.

Chairman of the South End Green Association, Elizabeth Knowles said: “The police and the bank have not acted and we thought that potential victims should be aware that there is a possible problem here and they should be on the look-out for it.

“It’s a case of if no-one will take action then the community will have to look out for itself. Also we hope it will deter the thieves from coming back.”

Elke Schulkes was stung by the ruse when she tried to take out �400 from the cash point last month.

A whirring noise from the ATM raised her suspicions and she dialled 999, but the 48-year-old was told to contact her bank to report the problem.

Mrs Schulkes, from Parliament Hill in South End Green, scratched away at the cash dispenser and a strip of metal with double-sided tape came away in her hand.

Her cash was sitting just inside the machine.

Mrs Schulkes, who handed the device into Hampstead Town Police Station, said: “It was stuck with some very strong glue so the money cannot escape the machine.

“It is done very professionally, making it very difficult to notice.

“The machine comes up with the message that the machine is out of order, or that it cannot serve you at this time and a lot of people could be tricked by this scam.”

Jonathan Bergman, chairman of the South Hill Park Watch for Safer Neighbourhoods, said: “This Barclays cashpoint provides a risky hit and miss method, but the cash point service is vital to the Hampstead Heath community.

“The bank needs to step up to this challenge of identifying thieves, providing greater safety for customers and money, making it too damn awkward and difficult for thieves to bother.”

A spokesman for Barclays said: “Unfortunately fraud is a problem for the whole of the banking industry and we have recently seen a different type of attack on a small number of our ATMs.

“We advise customers to always be vigilant when using their bank cards - for example be wary of anybody who is nearby or approaches when you are using the ATM, watch out for signs that the ATM may have been tampered with, and always shield your PIN.

“If your card or cash is withheld or you notice any suspicious behaviour please notify your bank straight away.

“Barclays customers should call 0870 010 4503 so that their card can be blocked immediately.

“If a customer is an innocent victim of fraud, we will ensure that they are refunded any losses.”