St George Bank has suffered a heavy fall in its satisfaction rating among business customers, according to the latest TNS business banking customer satisfaction report.Over the six months to March St George's satisfaction rating dropped 10.3 per cent to 74.4 per cent. All the big banks lost ground over the period but St George's is the biggest decline. National Australia Bank's rating fell 8.6 per cent, Westpac's 7.3 per cent, Commonwealth's 6.5 per cent and ANZ's 5.6 per cent.On a six-month rolling average ANZ is top of the TNS survey among the majors, with a satisfaction rating of 77.7 per cent. St George is second with a rating of 74.4 per cent, followed by Westpac, with 73 per cent, Commonwealth with 70.9 per cent and NAB with 70.1 per cent.The TNS report does not include qualitative responses, so it is not known why St George, long a favourite with business customers because of the strength of its relationship management model, has lost so much ground.