People are being urged to do research on websites before they shop online as two major banks report a surge in complaints about credit-card fraud and transaction disputes.
Netsafe chief executive Martin Cocker said there had been a steady rise in scams and fraud associated with online shopping.
"Consumers are looking to buy online and spending more money there and creating more opportunities for criminals."
As people made more online transactions it became more difficult for banks to monitor spending and identify unusual purchases.
"They do cop the cost of a lot of online fraud back into their business so they've got a real incentive to combat online fraud."