Shopkeepers were put on Christmas alert today after the seizure of £600,000 sterling of counterfeit money in Northern Ireland this year.
Traders in border areas were also warned because of the discovery of fake euro notes.
Chief Insp Mark Mason said: "The counterfeiters want to dupe everyone and their products are now of a quality that cursory check of a note is not sufficient".
Retailers have been urged to train staff as part of moves to try and detect the fake notes.
An estimated £14,000 of counterfeit money was recovered in 1995 when police investigated 428 reports.
But last year in Northern Ireland the figure soared to almost 2000 and with £600,000 in notes already detected this year, officers believe the amount will increase significantly during the Christmas sales rush.
People innocently caught in possession of the notes will have to bear the loss, police said.
PA