There were more than 20,000 reported phishing incidents in the first half of 2008, an increase of more than 180% from the same period last year, according to figures from UK payments association Apacs.
Reported phishing attacks increased to nearly 26,000 in 2007 from 14,000 the year before. But despite this rise, reported losses to online banking fraud fell last year by 33% to £34 million, says Apacs.
Apacs says each phishing attack involves thousands, or even millions, of spam e-mails being sent out.
Sandra Quinn, director of communications, Apacs, says customers need to be vigilant, particularly as the recent introduction of the UK's faster payments scheme will lead to an increase in the number of people conducting transactions online.
"The fact that the number of people banking online now exceeds 21 million is testament to how easy, convenient and safe this way of banking is. In the future we expect more and more people to use online banking to make payments rather than just checking balances, particularly in light of the recent introduction of the new faster payments service," says Quinn.
The Apacs stats also show that the number of Brits using Internet banking services hit 21 million in 2007, an increase of 505% since 2000.
The number of UK adults using online banking has increased from less than 3.5 million in 2000 to just over 21 million in 2007.
But the Apacs Internet banking figures are considerably higher than numbers published recently by analyst house Gartner which suggested that 26% of customers - around 14 million adults - now bank online.
In November Forrester Research found that, after a steady take-up of online banking services between 2000 and 2005, growth has slowed in the last two years and is set to remain sluggish as customers stick to using branches and ATMs.