Cambridgeshire Police is investigating what it describes as "a deliberate attempt" to affect its services, after being inundated with phone calls when its number was listed in a hoax email.
The email claims to be an invoice for a 40GB iPod music player and tells the recipient that their credit card will be debited £399.95. It then directs customers with questions to call a 'customer services' number.
But the number is the general enquiries line for the main police headquarters in Cambridge.
A search of Companies House reveals no sign of the company which claimed to send the email, Huntingdon Mail Order, and the delivery address of 47 Silver Street, London, NW1 5TR does not seem to exist.
vnunet.com reader Ben Eveling received one of the emails. "This sort of thing makes me really angry. Initially I thought 'lovely someone's bought me a prezzie'. Then I thought no one is going to spend £400 on me," he said.
"I was then concerned that somehow my credit card details had been stolen. The Cambridgeshire Police receptionist told me that the number of phone calls it was getting about this was no longer a joke."
Cambridgeshire Police said in a statement: "We are warning people across the country about an email that has been sent today advising people that they will have almost £400 removed from their bank accounts."
Deputy Chief Constable Alan Given said: "This appears to be a deliberate attempt to affect the service provided by the force.
"If you received such an email we would advise you to ignore it and not ring the customer services number that is listed."
But Given warned people who get the email to monitor their bank statement and to contact their local force as soon as possible if a similar amount is missing.
"It is too early to say who might be behind this or why they are doing it, but we will obviously be investigating," he said.
PUBG news and updates: November's Update #23 to bring new Skorpion pistol and changes to blue zone visibility
Genuinely useful side-arm coming to PUBG in Update #23
Asda, Morrisons and Tesco in the frame for checkout facial recognition technology
Research opens up new possibilities for structural batteries, where the carbon fibre forms part of the energy system
Another shape could have indicated hard-to-detect particles