Another pensioner has fallen foul of a telephone scam which is sweeping across north Essex.

Police have issued an urgent warning to residents in the area to be on their guard against telephone fraudsters after two incidents in two days in which elderly victims lost a total of £15,000.

A woman in her 70s at Saffron Walden was tricked into handing over £5,000 on Monday and a man in his 70s in the Steeple Bumpstead area fell victim to the scam and handed over £10,000 on Tuesday.

In both cases the victims were contacted by a man claiming to be a Metropolitan Police fraud squad officer based at Hammersmith who said he was investigating fraud at their respective banks.

The trickster claimed that he needed a large sum to be withdrawn from the local branches of the bank so that the banknotes could be forensically examined.

Chief Inspector Richard Melton, the Uttlesford and Braintree district commander, said: “These are despicable crimes being carried by thieves posing as police fraud officers, the very people they ought to be able to turn to and trust in exactly this sort of crime.

“Instead, they callously prey on the elderly and vulnerable and have no thought for how their victims might suffer from the loss of money that might have been saved over many years.”

Six other people in Uttlesford, four at Saffron Walden,one at Clavering and one at Stansted Mountfitchet, were contacted within a short space of time on Monday afternoon. Fortunately they realised they were being targeted by tricksters, ended the calls and contacted Essex Police.

More than 600 similar thefts and attempted thefts have been reported in Essex since the scam first came to light in January 2013, and similar crimes have been reported in the Met Police area and other counties.

More than 90 people in Essex have been tricked out of money and the total stolen is more than £325,000. Six people have been arrested in connection with the investigation.

Extensive publicity campaigns have been carried out across Essex to warn residents of the scam and although success thefts have reduced, elderly and vulnerable people are still falling for the scam.

Most of the thefts or attempted thefts have been in the west and south of the county but the sudden shift to the north and more rural communities of Uttlesford and Braintree districts has resulted in urgent warnings from Essex Police.

Chf Insp Melton said: “All of the eight people who were contacted on Monday and Tuesday were called by a man claiming to be a Met Police officer based at Hammersmith.

“Six of the people quickly realised it was part of a long-running scam but two people were convinced that they had to withdraw large sums of cash to help with a police investigation. The money was then collected from their homes but was not returned.

“It is vital that whenever people receive this sort of call they should put the phone down and call us, but on another phone or mobile. Part of the con involves keeping people on the line while they pretend to transfer calls to police officers or bank officials.”

CI Melton said that warnings about the fraud are being issued across the north of county using local media, Neighbourhood Watch groups, community forums and by PCSO and patrolling police officers stopping and talking with people who might be considered at risk.