Almost 20 million shoppers are now able to buy goods by simply waving their card in front of a reader at the tills, even if it is still in a wallet or a purse.
But industry experts have warned that the information emitted by the cards can be stolen by fraudsters using handheld receptors that cost as little as seven pounds on the internet.
It means cardholders, most of whom are given a contactless card automatically when their old one expires, can unknowingly surrender their personal bank details to a thief by simply walking past them in the street.
The technology in the card, known as radio frequency identification (RFID), transmits bank details via its own radio signal, and is accepted in many High Street chains, including Co-op, Boots and Pret-a-Manger, according to the newspaper Sunday.
It does away with the need for a customer inputting their PIN when buying goods, and was designed to reduce queues at the checkout.