Financial fraud losses increased by 25% in the first six months of 2016 - with scams and online attacks helping to drive the figures up, according to Financial Fraud Action UK (FFA UK).
Fraud losses across payment cards, remote banking which covers online and telephone banking and cheques amounted to £399.5 million in total in the first half of the year, marking a 25% increase on the same period in 2015.
FFA UK said banks' security systems continued to prevent the majority of fraud taking place, with £6 in every £10 of attempted fraud being stopped.
The body recently launched a campaign called Take Five, encouraging people to pause and think if they are asked to hand over any personal details about themselves or their financial arrangements.
Katy Worobec, director of FFA UK, said: "Banks use a range of robust security systems to protect their customers, but as these systems become more sophisticated, criminals have increasingly been turning to scams and exploiting data breaches to con victims out of their personal and security information, as well as money."
FFA UK is urging customers to be vigilant when receiving any cold calls or unsolicited text messages and emails and to be extremely cautious about giving out any personal and security information unless they are absolutely sure they know who they are dealing with.
It said someone's bank or the police will never call them to ask for their online banking passwords or four-digit card Pin, or to transfer money to a new account for fraud reasons.
FFA UK, whose members include banks and card companies, also urged all organisations that hold personal and financial data to improve their security systems in order to prevent data breaches.
It said retailers selling goods remotely can use a number of tools to build up a profile of their customer, verify the cardholder and ensure they receive payment securely.
It said anyone who thinks they have been a victim of fraud should contact their bank and Action Fraud immediately.
Tony Blake, senior fraud prevention officer at the Dedicated Card and Payment Crime Unit, the FFA UK-sponsored police unit which investigates fraud, said: "Fraudsters can be very convincing and often pose as representatives from a trusted organisation in order to appear genuine.
"If you are asked to transfer some money or provide your personal details and you think it could be a scam, take five minutes to think about what you are being asked to do.
"A genuine organisation will not mind if you check who you are speaking to, because people are not always who they say they are."