The FOS has published complaints data for the first six months of this year. The FOS took on around 170,000 new cases in the first half – a 13% increase in complaint figures compared to the last six months of 2016.

Almost two thirds of the complaints the FOS received in the first six months of this year come from just 10 businesses, nine of which are banks.

Payment protection insurance (PPI) continues to dominate the FOS’s workload with almost 90,000 complaints, making up over half of all complaints to its service.

For complaints relating to investments, banks were still top of the list with Barclays Bank receiving the most at 305 complaints, with Santander and Lloyds next on the list with 213 and 201 complaints respectively.

Royal Bank of Scotland had 43 investment complaints out of a total of 3,326.

When it comes to specialist wealth firms, St James’s Place (SJP) has the most investment complaints with 36 and has the most overall for a wealth firm with 71 complaints.

Hargreaves Lansdown Asset Management had 30 investment complaints out of a total of 50.

Close Brothers also features on the list with 169 complaints, but its complaints are related mostly to banking and credit with none related to investments.

Caroline Wayman (pictured), chief ombudsman and chief executive of the FOS, said: ‘We've seen more complaints about most types of financial products in the first half of 2017.

‘The FCA (Financial Conduct Authority) 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.

‘It’s free to come to the ombudsman – if you’re unsure what to do, get in touch and we’ll see if we can help.’