As many as 57 million US internet users have received phishing emails, with the attacks costing US banks and credit card issuers about $1.2bn last year.

Based on a survey of 5,000 adult internet users, analyst Gartner estimates that 30 million US users believe they have experienced a phishing attack, and another 27 million believe they have observed what looked like a phishing attack.

These scams involve emails that pretend to be from legitimate organisations, such as banks, in an attempt to steal personal information or bank account details.

Three quarters of the known or suspected attacks occurred within the past six months, Gartner said.

"Financial institutions, internet service providers and other service providers must take phishing seriously," warned Avivah Litan, vice president and research director at Gartner, in a statement.

"These service providers should take action to apply solutions that dramatically minimise, if not eradicate, the threat, even if the service providers themselves are not direct targets.

"Eventually, all participants in internet commerce will be hurt by an erosion of consumer trust in online transactions if phishing attacks are not sharply reduced from current levels."

Gartner estimates that about 19 per cent of those attacked - nearly 11 million US adult internet users - have clicked on the link in a phishing email.

And around three per cent of those attacked - an estimated 1.8 million adults - report giving phishers their financial or personal information.

UK banks have taken a more proactive stance in the past six months, with many routinely warning online banking customers of the latest scams.

To see some recent phishing examples click here.