Santander came next with 11,141 complaints followed by NRAM, the ‘bad bank’ cut away from Northern Rock when it was sold to Virgin, which racked up 7,863 complaints.

HSBC and Barclays took fourth and fifth position with 5,880 and 5,874 complaints respectively.

Bank of Scotland headed up the mortgage complaints table for H2 2013 when it received 15,075 complaints.

Bank of Scotland hit the headlines in August for double billing customers who had fallen behind on their mortgage payments which a Belfast judge described as ‘unconscionable’.

BOS was unavailable to comment.

The total amount of complaints received by the FCA for all product groups fell by 5% on the previous six months from 2,493,729 to 2,358,732.

Barclays was the most complained about bank overall with 278,426 complaints, a 10% decrease since the second half of 2013.

The FCA’s director of policy, risk and research, Christopher Woolard, said: “It’s important that firms now get on top of the issues that are driving complaints. Although it’s encouraging to see the total number of complaints fall, there is clearly further work to be done to ensure that consumer interests come first.”

PPI remained the most complained about product, with 1,236,899 complaints. This accounted for 52% of all complaints and 78% of complaints about general insurance and pure protection products.