Three of the Big Four banks, as well as Suncorp, all cut their standard variable mortgage rates by 20 basis points yesterday, in the wake of the RBA's Tuesday 0.25 per cent cut in the official rate.Westpac, the CBA and the NAB explained the 0.05 per cent difference from the official rate cut as being a product of the high cost of attracting and maintaining deposits, and continuing high wholesale funding costs.NAB retained its market position as the cheapest of the Big Four, at least on advertised rates. It cut its standard variable home loan rate to 6.38 per cent. The CBA dropped its standard variable rate to 6.40 per cent.Westpac's corresponding rate dropped to 6.51 per cent. But, reflecting the widespread discounts routinely offered on standard mortgage rates, Westpac said most of its standard variable-rate mortgage customers would move to a discount rate of 5.81 per cent.NAB's group executive for personal banking, Lisa Gray, said NAB "continues our delivery of our pledge to offer the lowest standard variable home loan rate of the major banks for 2012."NAB also cuts its rate on standard variable business-rate lending products by 0.2 per cent. Its UBank online subsidiary cut its standard variable home-loan rate by 0.2 per cent, to 5.27 per cent.ANZ will announce any moves it may make after its regular monthly rate review on 14 December.The wholesale-funded Yellow Brick Road was the only high-profile lender yesterday to cut its variable mortgage rates by 0.25 per cent.On Tuesday, ING Direct cut its loan and deposit rates by 0.25 per cent, and the Bank of Queensland cut its business and mortgage rates by 0.20 per cent.