The apparent generosity of the big three mortgage lenders is part of a rearguard effort to keep customers by making their standard variable rate mortgages more competitive. But it is unlikely to halt a steady exodus to aggressive rivals such as Bank of Scotland, National Irish Bank and Ulster Bank.

The European Central Bank's six interest rate hikes have added 1.5% to the cost of borrowing since December 2005. But Bank of Ireland has raised its standard variable rate by only 1.24%, effectively carrying the cost of one of the rate increases itself.

AIB and Permanent TSB have raised their rates by 1.3%.

The result is that AIB has the lowest standard variable rate at 4.6%, followed by Bank of Scotland and EBS at 4.75%.

Bank of Ireland and Permanent TSB come next at 4.85%.

But these rates are considerably higher than the switcher mortgages offered by the competition, aimed at poaching the bigger banks' long-time customers.

Bank of Scotland offers switchers a discounted rate of 3.95% for two years if they borrow less than 75% of the value of their homes, rising to 4.5% thereafter. National Irish Bank gives a lifetime guarantee that its rates will track the ECB by 0.5%-0.59%, giving a current mortgage rate of around 4%.

These low-rate offers, combined with the willingness of some banks to pay the legal costs of moving, has resulted in a surge in mortgage switching.

Almost 20,000 home owners moved to a different lender in the first nine months of 2006, according to figures compiled by the Irish Bankers' Federation.

That amounted to 13% of all mortgages taken out during the period.