Detectives have issued an urgent warning to residents across Essex following a sudden surge in phone calls by fraudsters posing as police officers or bank officials.

Seven homes across west Essex were contacted by tricksters yesterday and two people were conned out of £9,000 and £7,000.

The incidents are the latest in a series of crimes in which mainly elderly people are targeted and tricked into revealing their bank details or handing over large sums of cash.

Nearly 800 similar thefts and attempted thefts have been reported in Essex since the scam first came to light in January 2013. More than 120 people in the county have been tricked out of money and the total stolen is more than £400,000.

The scams were considerably reduced in July and August after a series of arrests and the introduction of shorter hanging-on times on home telephones which prevented some scams form being carried out.

But since the start of September nearly 20 calls have been made to people in Essex with the spate of seven all being in the Epping Forest district. Four were in Loughton, and the others were at Epping, Theydon Bois and Abridge.

In all cases, the callers claimed to be officers from the Metropolitan Police claiming that their victim’s bank accounts had been infiltrated by thieves. They advised victims to pay money from their accounts into a safe account held by police. Two people paid £9,000 and £7,000. The other intended victims realised the callers were bogus and called genuine police.

Other calls since September 1 have been received in Colchester where the trickster claimed to be a crime reduction officer from Colchester police station, Shoeburyness, where a caller claimed to be from a bank, Grays, where the called claimed to be a Basildon-based police officer, and Epping, Wickford, Southend, Leigh-on-Sea and Westcliff all by men claiming to be Met Police officers.

DI Rob Huddleston said: "The fraudsters are trying different stories and tactics and in some cases they have phoned 25 to 30 times to try to convince their intended victims that they are genuine. Fortunately the majority of people have not been tricked but two people in Loughton did fall for the fraud. A woman in Epping almost lost a large sum but her bank raised the alarm when she tried to transfer money.

"Police would never ask you for your bank details or ask you to transfer or withdraw funds. If you do receive calls like these do not fall for their claims and just put the phone down immediately and call police on 101.”