NatWest bank has been forced to suspend some of its online banking facilities in the wake of an e-mail scam.
No money was lost as a result of the scam, the bank said
Customers at the bank had reported that they had been sent bogus e-mails asking them to divulge their personal details - a scam known as "phishing".
In response, the bank has suspended the ability to create new third party payments online.
"We have taken immediate steps to protect our customers," a spokeswoman for NatWest said.
"Nobody has lost any money as a result of our pre-emptive measures," she said.
"But we do urge any customers who have given information to these e-mails to contact us immediately."
She added that with new third-party payments and standing orders currently on hold, any fraudster who had managed to pick up a customer's personal details would not be able to move any money.
Anyone wishing to set up such payments will have to use other methods, such as telephone banking.
Several banks have been targeted by similar "phishing" scams in recent years, and NatWest said it had increased security on its website over the past year as a result.