The ABA found overcharging errors in 75% of cases and recovered 2.5m in refunds last year, with an average of 7,500 per audit. ABA audits firms with more than four years banking and offers a free consultation prior to recovery, which costs around 80 per year.

ABA, which works with the BPIF to prevent overcharging, was also disappointed with last weeks report by the Competition Commission, which said that banks had been making excessive profits of 725m a year from SMEs.

The report said the four largest banks Barclays, HSBC, Lloyds TSB and Royal Bank of Scotland Group "restrict and/or distort price competition and result in those clearing groups charging excessive prices".

It recommended that the banks pay interest on small business current accounts or scrap transmission charges.

ABA managing director Ian Foyster, who worked in the printing industry for 28 years, said: "The report doesnt ensure sufficient price transparency for the average small business owner to make a fully informed decision."

"Yet there is no indication in the report that banks will be making efforts to recompense customers they have ripped off all this time."

BPIF head of corporate and external affairs Cicely Brown encouraged members to take advantage of a 7% discount for ABA services.

A spokeswoman for The Royal Bank of Scotland Group said the Bank was still considering its response to the 1,386pp report.

Story by John Davies