NAB, ANZ least popular of Big Four

National Australia Bank and ANZ spent the last financial year trailing their major rivals in terms of satisfaction among business clients.

Hundreds of thousands of bank customers could benefit from the broadest class action in Australian legal history over credit card late fees worth hundreds of millions of dollars.

National Australia Bank and ANZ are the least popular of the big four banks as far as business customers are concerned.

A survey of satisfaction among the big four's business customers shows NAB and ANZ ranked below the Commonwealth and Westpac for every one of the past 12 months.

Commonwealth and Westpac finished the financial year with average business customer satisfaction ratings of 7.4 and 7.3 out of ten, respectively.

By comparison, ANZ and NAB both had an average satisfaction rating of 7.0 in June.

The DBM Consultants' Business Financial Services Monitor (BFSM) tracks customer service ratings among the big four clients on a monthly basis through interviews with 20,000 businesses annually.

DBM managing director Dhruba Gupta said Westpac and the Commonwealth had done a better job of keeping their customers happy.

"While all financial institutions have heavily invested in delivering improved customer service, business decision makers have consistently rated Westpac and the Commonwealth Bank highest, clearly appreciating the initiatives brought in by these banks," Mr Gupta said.

"This includes activities such as making relationship managers more accessible and returning calls within 24 hours."