The Defaqto annual survey reveals increasing competition between banks and building societies to offer cheap mortgage deals.
Although its research shows that the cheapest mortgage for existing borrowers in 2007 was offered by a bank, building societies accounted for two of the top five and five of the top ten lenders.
HSBC held its place at the top of the list of standard variable rate mortgages or equivalents for existing borrowers. However, Skipton Building Society and Nationwide were in second and third place, respectively.
According to Defaqto, HSBC's charges on an interest-only, £50,000 loan were £3361.99, while Skipton's were £3435.07 and Nationwide's were £3485.07.
The distinction between the top and bottom of the table was vast, with Bank of Scotland customers paying £3894.38, £532.39 more than those with HSBC.
The other seven companies making the top ten are: Intelligent Finance, Direct Line, Britannia, The One Account, Standard Life Bank, Yorkshire Building Society and Principality.
Principal banking consultant at Defaqto, David Black, said: "In 2007 there were three increases in Bank Base rates and one decrease, so it is not surprising that the average cost of servicing a standard variable rate mortgage for the largest lenders rose last year by 14 per cent over the cost in 2006."
"While it is acknowledged that standard variable rate mortgages are only one type of mortgage, their importance may be increasing due to the knock-on effects of the credit crunch, making it more difficult to obtain attractive alternative deals," he added.
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