Barclays Bank faced more controversy on Wednesday as it topped a watchdog's list of the UK's most-complained about banks, but gripes about financial service companies fell overall.Retail customers launched nearly 310,000 complaints against Barclays between July and December last year, the Financial Conduct Authority (FCA) said.The number fell 17% from the first half of the year, but remained about 50,000 more than second-ranked Lloyds Bank, part of Lloyds Banking Group.Barclays, which has undergone an overhaul after its involvement in the Libor-rigging scandal and other controversies, racked up 309,494 complaints against Lloyds's 256,656.Lloyds was the only bank in the top five in the list to register an increase in complaints during the period, up 1% since the first half of 2013.Barclays said the fall in complaints was encouraging, but pointed out that the FCA's figures failed to take account of complaints received by subsidiaries or sister businesses of other banks.Chief Executive of Barclays Retail & Business Banking Ashok Vaswani said:"Any reduction in the number of complaints made by our customers is welcome news. However, we recognise we still have a way to go, even one complaint is one too many."Credit card issuer MBNA, Lloyds-owned Bank of Scotland and National Westminster Bank, owned by state-backed Royal Bank of Scotland, were third, fourth and fifth respectively.People opened 2.48m complaints against financial services firms between July and December 2013, down 15% on the 2.9m complaints reported in the previous six months."No firm wants to top this particular list and they all should be striving to ensure they treat customers fairly and don't give them cause to complain," said FCA Chief Executive Martin Wheatley, releasing the latest complaints data.Wheatley said firms seemed to be improving, but added: "There is clearly more for us all to do to show consumers their interests come first."Most customer complaints still involve payment protection insurance, a mis-selling scandal for which banks have set aside more than £20bn for compensation claims, followed by grievances about other insurance products, current accounts, credit cards and savings.Meanwhile, Barclays is continuing its cost-cutting drive by moving more of its staff in Singapore to an office in the island-state's financial district from a site in a suburb known as Tampines, according to a report from financial news agency Bloomberg.About 300 people who work in back-office roles are believed likely to be affected.PW