Around a third of the UK's online population - 10.9 million people - accessed their bank account via the Internet in January, according to Web metrics firm comScore.
Lloyds TSB was the most popular individual brand online with 2.8 million customers. The bank also recorded the highest number of average visits to its site during the month, with 6.8 per customer in January.
Royal Bank of Scotland had 2.9 million online banking customers in the UK in January, of which two million accessed NatWest accounts. The average RBS online customer visited the bank's sites 5.9 times during the month.
Hbos and HSBC both received around 2.4 million online customers during January. Hbos customers visited the site slightly more regularly - 6.1 times compared to 5.2 for HSBC users. Barclays recorded 1.7 million visitors, using the site 5.9 times on average.
The figures back up research from analyst house Gartner which said earlier this year that online banking is now a mainstream access method for retail customers on both sides of the Atlantic.
The study found that 26% of UK customers - around 14 million adults - now bank online. In the US 33% of customers - the equivalent of 71 million people - regularly use Web banking services.