There are new fears that remortgaging may not be so financially beneficial as believed, due to the number of hidden costs.
Extras such as a valuation, compulsory indemnity insurance and arrangement fees can all add hundreds of pounds to the cost of a mortgage deal.
These are often forgotten by borrowers who only look at the rate of interest or the monthly repayments.
A spokesman for Nationwide, Joe Wiggins, says: "Remortgaging can potentially save borrowers a lot of money for very little effort by switching providers."
However, he warns that consumers must "watch out for lenders that do not provide free legal and valuation services or those that charge high reservation or arrangement fees as this can make a big difference to the upfront cost."
At present, many lenders do not charge fees when a customer remortgages with them.
For example, Nationwide waive the valuation fee for remortgagers - a fee that costs new buyers between £175 and £595.
Some lenders also offer cashback deals. But the danger with cashback is that while most are paid on completion of the loan agreement, many have to be repaid in some part as a redemption penalty if the borrower remortgages within a given period.DeHavilland Information Services plc