Some of the biggest mortgage lenders are increasing their fees to keep headline interest rates low, BBC Radio 4's Money Box has discovered.
On some deals, arrangement fees are up by as much as 50%
Dave, from South London, took out a discounted mortgage with the Northern Rock five years ago, attracted by an interest rate of 4%.
He told Money Box: " I was a first time buyer... It was a very good introductory rate... I suppose I was slightly seduced."
In August, with the discount period about to end, he changed his loan. But once he had signed up with a new lender he was told by Northern Rock he would have to pay them £225 to complete the transfer.
He says: "It feels really as though I've had my pocket picked."
Siobhan, from Northamptonshire, was charged £295 when she moved her mortgage away from Alliance and Leicester last month.
When she rang up to query the bill, she was told that it had gone up by £100 from £195 in August.
She told Money Box: "It's a lot of money to be parting with when the whole idea of changing to another mortgage is to reduce our outgoings every month."
In both cases, the fee was an exit penalty also known as a "deeds release fee" or a "sealing charge".
Ray Boulger of leading mortgage broker Charcol says lenders are exploiting the fact that these charges are not well publicised.
"These exit fees used to be typically around £100 to £125. Lenders can change them whenever they wish".
And it is not just paying to get out of a deal that is costing more.
Money Box has learnt that, over the past year, Nationwide, Halifax, Northern Rock and Britannia have all increased their "arrangement fees", the charge for buying a mortgage in the first place.
On some deals they are up by as much as 50%.
Ray Boulger says lenders are using additional charges like these to keep their interest rates low.
This gives them a higher place in comparison tables.
"Because of the way the best-buy tables are compiled... getting a good headline rate tends to be the most important fact behind getting a lot of business."
Jane Dawson of the online best buy site "Moneyfacts" recognises the problem.
"We do realise that arrangement fees... are a complicating factor... but we have to start somewhere... and the rate is the thing that people actually look for on a long term basis."
Meanwhile, the advice to those looking to change their home loan is to work out the cost of buying the mortgage, getting out and the interest over the time you intend to keep it.
However, those on smaller mortgages may decide it is not worth their while to change.
BBC Radio 4's Money Box was broadcast on Saturday, 9 October, 2004 at 1204 BST.
The programme was repeated on Sunday, 10 October, at 2102 BST.