Complaints about self-invested personal pensions had the highest uphold rate of any product looked at by the Financial Ombudsman Service in the first quarter of this year.
Figures released by Fos showed there were 427 enquiries about Sipps between April and June, making them the 29th most complained about product.
But 66 per cent of the 328 complaints about Sipps were upheld, a higher proportion than any other product.
Even payment protection insurance, which had the most enquiries and complaints at 53,045 and 43,569 respectively, only had an uphold rate of 57 per cent.
Payday loans was the only other product to come close, with an uphold rate of 55 per cent for the 2,729 complaints the Fos received.
Fos said: “We received a total of 81,709 new complaints about financial businesses - of which just over half were about payment protection insurance.
“Packaged bank accounts and current accounts continued to be the most complained-about products after PPI.
“The overall proportion of complaints we upheld in favour of consumers was 48 per cent.”
There were 2,620 complaints about house mortgages in the first quarter of 2015/16, 461 about personal pensions, 329 about portfolio management and 292 about investment Isas.
Annuities were the product with the lowest uphold rate, at 13 per cent for its 128 complaints, while the product with the lowest number of complaints between April and June was open-ended investment companies, which only received 34.
Meanwhile in the latest edition of Ombudsman News, in which today’s figures are published, chief ombudsman Caroline Wayman addressed the issue of Brexit.
She said: “While there are of course many things to be worked out for now at least it’s business as usual for us.
“The Financial Conduct Authority has said that, until the government and parliament makes changes, the regulation of financial services remains the same.
“As the picture develops, we’ll be keeping in touch with the FCA and others to talk about what the referendum decision could mean for our work.”
The Financial Services Compensation Scheme recently reported a dramatic spike in claims relating to poor advice given on non-standard investments held within self-invested personal pensions, and said the trend is likely to continue.
During the 2015 to 2016 financial year the paid out £83.8m on life and pensions claims, 92 per cent of which related to non-standard investments - such as unregulated offshore property - held in Sipps.
That was twice the 2014 to 2015 figure of £35.2m, which itself was twice the 2013 to 14 figure.
