Condom-maker Durex has recalled thousands of boxes of the product after bogus condoms were discovered on the shelves.
The fake prophylactics are 10 times more unreliable and have more holes than the international standard allows.
They have been found in "convincing" Durex-style packaging and are thought to originate from China.
Chris Bunniss, marketing director of Durex, said: "They are a very good match. The condoms are sub-standard but the packaging is very convincing.
"We believe they originated in China and whoever is doing this is ripping us off."
Among the batches that have been re-called are Durex Extra Safe 12 pack batch number 20602503 and Durex Fetherlite 12 pack batch number VR3073C.
One way of spotting the fakes is the poor printing quality on the boxes. The letter "C" at the end of the serial number looks like an "E" or a Euro sign.
On the condom foil itself, the batch number is printed as VR3073 followed by a "U".