Barclays Bank has reduced the daily payment limit on personal accounts to £500 in an effort to protect customers who have been duped into revealing their security details at a bogus bank Internet address.
The fraudulent e-mail advises Barclays' customers of a technical upgrade and points them in the direction of a look-alike Web site to update their personal account details.
Barclays says it is taking action to shut down the fraudulent Web site and has warned customers not to be fooled by the scam.
The bank says it has been contacted by 400 of its 3.5 million online customers who received the e-mail and that "a handful" of users had uploaded their details to the fake site.
Barclays says it will cover any losses incurred by customers as a result of the fraud. In an effort to stem the damage, the bank is temporarily reducing the daily payment limit for all accounts to £500.
The security scare is the latest in a rash of so-called e-mail phishing scams to be targeted at banks worldwide.