Building societies have been slow to pass on last week's interest rate cut with only four so far announcing plans to reduce their rates.
A total of 23 banks and building societies out of 85 have so far said they will be reducing their standard variable rate (SVR) following last week's 0.5% reduction in the Bank of England base rate.
But only four of these have been building societies, namely, Nationwide, Britannia, Melton Mowbray and Beverley.
Building societies also account for half of the four lenders who have said they will not be passing on the full 0.5% reduction.
Nationwide is reducing its SVR, which it calls the base mortgage rate, by 0.3%, while Beverley is cutting its equivalent by 0.2%, although both groups still offer some of the lowest SVRs available at 6.19% and 6.2% respectively.
Louise Cuming, head of mortgages at moneysupermarket.com, said: "Mutual organisations are supposed to put their members first, but they clearly haven't in the past week.
"People on SVRs are traditionally those who have struggled to get a mortgage, so they are in even greater need of some relief.
"Because building societies don't have shareholders to satisfy, they can afford to offer much better terms to their customers - this is what their whole model is based on. They have also not been crippled by the bad debt crisis to the same extent as some of the bigger banks."
But Michelle Slade, of financial information group Moneyfacts.co.uk, said: "Building societies usually take a bit longer because they have a lot of products linked to their SVR, but they usually pass on the reduction."
Mortgage rate cuts also generally only come into force from the first day of the following month, meaning building society customers will not necessarily lose out because mutuals are taking longer to announce their intentions.
Meanwhile, two major lenders announced they were raising the cost of their tracker mortgages for new customers.
Lloyds TSB said it was the increasing the cost of its mainstream trackers by between 0.3% and 0.5%, while Barclays' lending arm the Woolwich is raising its lifetime and offset tracker rates by 0.2%.
The Woolwich reduced the cost of its tracker deals by 0.5% following last week's Bank of England base rate cut.
But Lloyds, which also lends under the Cheltenham & Gloucester brand, failed to do this, meaning the differential between the cost of its deals and the base rate has risen by between 0.8% and 1%.
Both groups blamed their decision on recent rate increases made by competitors.
Part of the problem for lenders is that wholesale money markets have failed to respond to last week's interest rate reduction.
The key inter-bank lending rate, three month Libor, upon which many variable rate mortgages are based, has remained stubbornly high despite the 0.5% fall in the official cost of borrowing.
It edged down by four basis points yesterday, but still stands at 6.21%, well above the Bank of England base rate of 4.5%, as banks continued to be reluctant to lend to each other.
But on a brighter note the number of different mortgage products available has increased slightly to 3,288.
There has also been a more dramatic increase in the number of lenders prepared to advance funds to people who have only a 5% deposit, with 76 different deals now available for people looking to borrow 95% of their property's value, nearly double the 43 that were available just a week ago.