The Ombudsman received 21,348 complaints about the accounts – which tend to be paid for and include bolt-on extras such as insurance policies and motor breakdown cover – up from 5,667 a year earlier.

Packaged accounts have in the past been criticised by the regulator. It introduced new rules in 2013 forcing banks to check the eligibility of customers before selling the products.

Payment protection insurance (PPI) disputes halved over the last year but still made up two thirds of the Ombudsman’s workload in 2014/2015.

The number of PPI complaints fell to 204,943, from record highs the year before. But 63% of all new complaints were about the sale of these products.

In total, the Ombudsman answered 1,786,973 enquiries from consumers – around 5,000 each working day.

Chief ombudsman, Caroline Wayman, said: “The world has moved on and changed significantly since I first joined the ombudsman as an adjudicator in 2001. Yet our workload over the last 15 years has been constantly dominated by the past – clearing up the fall-out of the mass claims and mis-selling scandals of the last decade and a half.

“But 15 years of sorting out millions of these problems have given us unparalleled experience, knowledge and understanding of why complaints happen – and how they could be avoided in future. That’s why our focus continues to be on complaints prevention and sorting things out pragmatically as soon as problems emerge.”