The group received 20,541 new complaints, with the majority (17,080) related to PPI. For pure banking and credit services, Barclays Bank received the most complaints (6,192). Mortgage and home finance complaints were generally low, but NatWest and Nationwide topped the charts there with 347 and 299 complaints respectively.

The complaints data relating to banks, insurers and other financial businesses show a total of around 170,000 new cases in the first six months of this year, representing a 13% increase over the previous six months. Almost every product sector saw a rise, including PPI and banking.

The Ombudsman said that almost two thirds of the complaints it received in the first six months of this year come from just 10 businesses. PPI continues to be the most complained-about product with almost 90,000 complaints – making up over half of all complaints to the service. That said, complaints about banking and credit have increased by 12% to around 47,000.

Caroline Wayman, chief ombudsman and chief executive of the Financial Ombudsman Service, says: “We’ve seen more complaints about most types of financial products in the first half of 2017.

“The FCA has just launched its communications campaign, which highlights that consumers have until August 2019 to make a complaint about mis-sold PPI. While we still don’t know what impact this will have on our workload, today’s data shows that PPI complaints are already increasing.”

Top 10 most-complained about businesses

1. Bank of Scotland – 20,541
2. Lloyds Bank – 18,068
3. Financial Insurance Company Ltd – 12,044
4. HSBC – 9,044
5. Capital One – 7,402
6. Santander – 6,271
7. NatWest – 5,929
8. Nationwide – 4,777
9. MBNA – 4,368
10. The Royal Bank of Scotland – 3,326