Schools were warned today to watch out for fraudsters flogging bogus advertisements in one of Britain's best-known telephone directories.
Trading standards officials have uncovered a gang of conmen posing as representatives of Yellow Pages.
Working under the name The Yellow Pages 24, they have been tricking victims into spending £499 or £599 on non-existent products.
Officials in Westminster, London, have already seized cheques worth almost £10,000 sent in from duped staff at schools and colleges across Britain.
They believe institutions in Lincolnshire, Kent, Somerset and Shropshire, as well as Scotland and Wales, have been targeted.
Sue Jones, of Westminster City Council, said the received money could be the "tip of the iceberg".
She said: "The fraud is simple, yet has proved highly profitable for those behind it who appear to have been consistently targeting schools, colleges and businesses across the country.
"Busy school staff would not suspect they're the victims of a widespread and systematic fraud as some advertise with Yellow Pages anyway, so when an invoice purporting to be from the company arrives they diligently pay the bill.
"But it is essential all businesses are confident they are dealing with a legitimate firm before parting with their money."
Officials warned staff to be on their guard for unexpected invoices from companies with slightly altered names after receiving hundreds of complaints.
In some cases victims were harassed with threatening phone calls demanding people sign forms to cancel an advertisement they did not order.
Bogus invoices are sent to victims, who pay money into a German bank account or send cheques to an address in Oxford Street.
A spokesman for Yell, publisher of Yellow Pages, said the company has won a High Court injunction against The Yellow Pages 24, shutting its website and fax.
He said: "We take our responsibilities for consumer protection very seriously and as a responsible company are committed to supporting and protecting the users of our products and services and our advertisers.
"We don't hesitate to take legal action if necessary to protect our brand and safeguard our registered trademarks."
Daniel Astaire, of Westminster City Council, said: "This crime is depriving schools and colleges of funds which could pay for extra resources for pupils.
"We are doing all we can along with law enforcement agencies to help track down those responsible and bring them to justice."
* Anyone who suspects they have been targeted should contact Consumer Direct on 0845 4040506.