The lender reports that there may now even be a plc gap, where borrowers using building societies are paying over the odds compared to customers with plcs.
Nine of the ten largest building societies have widened their margins since March this year, and 62 of the 66 building societies currently have a higher variable rate than the Halifax, according to the lenders research.
Paul Duffin, head of mortgages at the Halifax, said: “Some building societies have claimed that they are inherently more competitive than their plc counterparts. Nothing could be further from the truth. This research just how busy some building societies have been recently widening their margins at the expense of their customers.”
