Unsuitable advice was the single biggest cause for complaints to firms in the financial services sector, according to the Financial Conduct Authority.
There were a total of 3.32m complaints about financial services in the first six months of 2017, the FCA has said.
Of these 29 per cent – or 951,171 – were related to unsuitable advice, with general admin and customer services being the next biggest category at 19 per cent, or 616,463 complaints.
Despite this the proportion of complaints lodged because of “advising, selling or arranging” fell to 43 per cent from 59 per cent in the same period during 2016.
Christopher Woolard, the FCA’s executive director of strategy and competition, said: “We now require firms to report all complaints which gives us a fuller picture of where the industry might not be meeting customer needs.
“But even allowing for the change in reporting rules, and some progress made, the numbers are still significant.
“Firms need to do all they can to reduce complaints and ensure that they are working in the best interests of consumers.”
The advice firm which received the most complaints was St James’s Place, which between its two divisions received 1,289 complaints.
The largest number of these – 465 – were submitted to St James’s Place UK and related to decumulation and pensions but these accounted for only 1.6 complaints for every 1,000 policies in force.
Sesame was the firm with the second highest number of complaints, at 665.
The big five banks received the most complaints, with Barclays taking the top spot with 446,978.
Old Mutual Wealth received 1,379 complaints while Standard Life received 3,579.
Hargreaves Lansdown received 2,104 complaints, with 2,014 of these about investments - three for every 1,000 client accounts.
The company with the most complaints about decumulation and pensions was Prudential with 9,408 - or 2.7 for every 1,000 policies - while the one with the most about investments was Barclays with 3,879 - or 8.7 for every 1,000 client accounts.
Bank of Scotland received most complaints about home finance at 21,955 - or 8.6 for every 1,000 balances outstanding.
When broken down by the number of complaints per account, Alliance Trust Savings received most for pensions and decumulation, with 33.1 for every 1,000 policies in force, while The Co-operative Bank received most for investments, with 136.8 for every 1,000 client accounts.
Paragon Finance received 43.1 complaints for every 1,000 balances outstanding, more than any other home finance provider.
Payment protection insurance was the single most complained-about product, accounting for 1,11m complaints, making up a third of the total.
The total redress paid out was just under £2bn, with 82 per cent of this being for PPI complaints.
damian.fantato@ft.com
