The increase comes despite the Bank of England cutting the bank rate by 2 per cent during the same period.
It means the gap between the bank rate and the rate that a borrower pays on a loan has almost doubled in just over two months from 2.92 per cent to 5.36 per cent.
The figures are the latest evidence of how families are being affected as lenders try to recoup lost profits amid the credit crisis.
Tim Moss, head of loans at moneysupermarket.com, said: "While personal loans are often seen as the 'poor man' of everyday financial products, there is always a spike of activity post-Christmas and into the New Year when consumers take their finances in hand, and turn over that new leaf. Invariably this involves consolidation of store cards, credit cards and overdrafts. But loans are not the cheap form of borrowing they once were."
He added, however, that rates on personal loans might decline after Christmas as providers try to attract those with New Year financial resolutions.
Borrowers are urged to keep a close eye on the best deals and ensure they only apply for products they're likely to be accepted for to keep their credit record as clean as possible and not taint it with failed applications for loan.
Hugo Shaw, of independent financial advisers Bestinvest, said: "Undoubtedly some lenders will try and take advantage of borrowers by not passing on the full effect of recent cuts in base rate. However, with household costs having jumped so much in the last year and the threat of redundancy hanging over many people, lenders will be getting increasingly concerned borrowers will default on unsecured loans.
"In the current climate it will pay to protect your credit rating - gone are the days for cheap credit for those whose credit histories are rather too colourful."
A spokesman for the British Bankers' Association said: "Banks are still offering competitive personal loans and with loans, as everything else, it pays customers to shop around for the deal that suits them best.
"The interest banks charge will reflect a number of things - not just the base rate over which customer rates have always been set. These include staff and administration costs which have all gone up as well as the need to take risk into account."
If you feel that you need help
