National Australia Bank has suffered a heavy fall in customer satisfaction over the past year, putting it at the bottom of the pack among the Big Four for the first time since 2011.According to the latest Roy Morgan Research consumer banking customer satisfaction survey, NAB's rating fell 3.3 percentage points over the 12 months to May to 78.5 per cent.It ranks behind ANZ, which has a satisfaction score of 79.1 per cent, Westpac (79.2 per cent) and Commonwealth bank (81.7 per cent).NAB's previous chief executive Cameron Clyne, who was in the job from 2009 to 2014, placed considerable emphasis on reputation and customer satisfaction. He was also keen to see the bank grow its share in retail banking.When Clyne took on the top job at NAB, the bank's customer satisfaction was the lowest of the big banks and trailed the others by a considerable margin. The bank launched its Break Up campaign in 2011, seeking to differentiate itself from the other big banks by cutting retail banking fees and interest rates.By the end of 2012 it had the top rating among the Big Four and it competed with CBA for the top position through to 2015.Clyne was succeeded in August 2014 by Andrew Thorburn, whose priorities have been to sell NAB's UK subsidiaries and re-establish the bank's pre-eminent position in business banking.Coincidentally or otherwise, the bank's fall from grace with its retail customers has been a feature of Thorburn's incumbency.Among the other financial institutions in the survey, Teachers Mutual Bank had the highest satisfaction rating, with a score of 94.5 per cent, followed by Heritage Bank (93.5 per cent) and Bank Australia (93.1 per cent).Leading the way among banks whose customers are likely to recommend their bank to others is ING Direct. The bank's satisfaction rating is 89.3 per cent but 79.7 per cent of its customers are likely to recommend it.Roy Morgan's measure of "high likelihood of recommending a main financial institution" is a score of eight or more on a ten-point scale.Others that scored well on that measure include Bendigo Bank (69.5 per cent), Bank of Queensland (65.1 per cent), Suncorp (62.6 per cent) and Bankwest 61.2 per cent.