The figure represented complaints across all products offered by Barclays but most complaints were made against its banking practices, with over half the banking complaints (52 per cent) upheld.
Of the high street banking giants Santander came second in the customer grievance stakes, receiving 195,475 complaints in the second half of last year, while Lloyds TSB received 175,892 complaints and Bank of Scotland received 123,477.
Meanwhile Natwest received 118,765, HSBC 80,794 and Royal Bank of Scotland 53,806.
During the same period the amount of redress paid out by banks and building societies rocketed by 14 per cent to £342m, up from £301m in the first six months of the year according to figures released by the Financial Services Authority (FSA).
Total overall complaints across all financial products and institutions increased by three per cent to 1,795,182 in the second half of the year. However this was dominated by a 37 per cent increase in complaints about general insurance and life protection.