Contactless cardholders who cancel their cards after having them stolen are still at risk of fraud, it has emerged, as the process does not always stop them being used by thieves in shops.
An investigation by consumer website moneysavingexpert.com discovered cancelled cards being used up to eight months later by criminals to buy items in shops.
People whose contactless cards have been lost or stolen are being told to comb through months or years's worth of statements to check for fraudulent transactions which may not have been flagged by their bank.
The problem is borne from a tap-and-go technology loophole which lets thieves make so-called "offline" payments without the bank which issued the card being informed.
The only way to detect such payments is by going through people's bank statements.
Offline payments are stored in batches by retailers and processed online to the bank at a later point, sometimes a few days later with smaller stores. This can allow a thief buying goods on a stolen card to go unnoticed.
Other payments - often in larger stores - are processed online which means the card and payment machine immediately communicate with the customer's bank.
If a lost or stolen card has been cancelled, this will be flagged immediately and a payment not allowed.
As a safety measure some firms set a "floor limit" at which payments are forced to go online - meaning anything above a certain amount is checked out immediately with the issuing bank.
The report from moneysavingexpert.com said the "chaotic system" means that while some accounts are prevented from being raided by this type of fraud, in other cases it is left to customers to spot dodgy payments.
Contactless card use has grown rapidly in recent years as a handy alternative to cash. A year ago, the contactless card limit for a single transaction was raised by £10, to £30.
In March, contactless card spending in the UK topped £1.5 billion in the space of a month for the first time.
A spokesman for the UK Cards Association said: "Fraud on contactless cards is rare and considerably lower than overall card fraud. Consumers are fully protected against any fraud losses and will not be left out of pocket.
"As always it is important to check bank or card statements regularly for any unusual transactions, especially if a card has been lost or stolen. When a customer reports a lost or stolen card they will be advised to report any transactions they do not recognise to their bank."
Source: The Telegraph