Hertfordshire residents have been duped out of nearly £50,000 by fraudsters posing as police officers, amid a national spike in scam phone calls.

In October, victims living in Baldock, Letchworth and Ware received calls from a man claiming to be a DC Robson from the Metropolitan Police - and handed over a total of £18,000.

During the same period, four victims from Hatfield were contacted by someone claiming to be a DC Taylor and handed over £20,000, while 12 victims - living in Hatfield, Watford and Welwyn Garden City - received calls from a man pretending to be DC Martin Rose from Watford Police Station and have lost approximately £10,000.

Victims are called by fake police officers who ask them to provide bank cards and PIN numbers for collection by a courier.

The fraudsters will often ask the victims to call back on 999, 101 or 161 - in an effort to appear genuine - but then keep the line open so that the victim continues to speak to the fraudster.

Detective Inspector Rob Burns, from Herts police Serious Fraud and Cyber Unit, said: "The fraudsters are extremely convincing and persistent and often target the elderly or vulnerable resulting in the loss of thousands of pounds.

"It's important to remember that police officers and bank officials will never ask you to withdraw money, purchase goods or hand over private banking details.

"Please help us to raise awareness by sharing this with your friends and family, especially if they are vulnerable or elderly."

If you believe you are a victim of this scam, please contact Herts police's non-emergency number 101 using a different phone to that targeted by fraudsters.

Herts police also offer the following crime prevention advice:

- Be sceptical of callers, even those who claim to be officials.

- Don't be afraid to put the phone down with a brief 'No, thank you'.

- NEVER give personal information, such as your date of birth or bank details, to unexpected callers.

- Remember that the police or your bank would NEVER unexpectedly call you and ask you to withdraw cash or move your money to another account, as a result of fraud or any other reason.

- If callers suggest you call your local police or bank to check who they are, use another phone or ensure the line has been fully disconnected by phoning a friend or relative first, or by waiting at least five minutes, otherwise you may think you've phoned a number, but you're simply talking to the fraudsters again. This is a common fraudsters' tactic.

- If a caller asks you to type your bank PIN number into your telephone handset do not do this, as fraudsters can use technology to identify the numbers.

- You can opt out of many cold calls by registering for free with the Telephone Preference Service on 0845 070 0707.