A warning has been issued after a police calling scam has seen St Albans, Harpenden and Welwyn residents lose more than £30,000.

The victims received phone calls from people claiming to be police officers investigating fraudulent activity on their bank accounts.

They were then asked to withdraw cash to hand over to a courier who was despatched to their addresses by the fraudster.

Seventeen residents have been targeted around the county since the start of April, including people from Harpenden, St Albans and Welwyn, with more than £30,000 lost in total.

"Fraudsters have been targeting victims with this scam for several years, some of whom have lost thousands of pounds," said Detective Inspector Pete Hankins, from Hertfordshire Constabulary’s Serious Fraud and Cyber Unit.

"The fraudsters use different stories to convince people they are genuine, in this case using officers’ names of Harris, Rotha and Kent from Hammersmith Police Station.

"The important thing to remember is that police officers or bank staff would never ask for people’s bank details, like a PIN, or for cash to be handed over. You should never give your bank details to anyone.

"Usually the intended victim realises the call is not genuine and refuses to part with their details or cash.

"However, these fraudsters can be very persuasive and insistent, which has resulted in some people falling victim to this scam and subsequently losing thousands of pounds from their accounts."

If you are not happy with a phone call and are suspicious of the conversation you have with the caller, then you should end the call and dial 101 or report online herts.police.uk/report.

When reporting a suspicious phone call to police, wait at least five minutes before attempting to make the call to ensure you’re not reconnected to the offender.

Alternatively, use a mobile phone or test your landline by phoning a friend or relative first, to ensure you aren’t still unwittingly connected to the offender.

If you have concerns about your bank account, visit your local branch.