Sesame received the most Financial Ombudsman Service complaints between January and June with nearly a quarter of its 160 complaints upheld.
The FOS released its six-monthly complaints data today, including the five advice firms that received the most complaints.
Sesame topped the list and also saw an increase in the number of complaints from the previous six-month period when 116 complaints were filed against the company and 23 per cent were upheld.
Openwork was the second most complained about advice firm between January and June, but it received half the number of complaints as Sesame in the period. Of the 80 complaints made about Openwork 24 per cent were upheld.
St James’s Place was third with 58 complaints, of which 24 per cent were upheld, followed by Positive Solutions which had 30 per cent of its 34 complaints upheld.
Hargreaves Lansdown was fifth on the list with 33 complaints and an uphold rate of 13 per cent.
The FOS took on 169,132 new cases in the first half of 2016 – an increase of 3 per cent on the previous six-month period.
The average uphold rate between January and June was 48 per cent, ranging from 3 per cent to 92 per cent across the individual businesses.
Lloyds Bank, Bank of Scotland and Barclays were the top three most complained about businesses overall.
Lloyds received 22,241 complaints, of which 70 per cent were upheld, Bank of Scotland 22,090 complaints, of which 34 per cent were upheld, and Barclays 18,603 complaints, with 47 per cent upheld.
HSBC and NatWest were also in the top five most complained about business with 11,082 and 8,027 complaints respectively.
Chief ombudsman Caroline Wayman says: “The data we have published about complaints over the last decade or so helps to illustrate a challenging and volatile period for financial businesses. But the current signs are that complaints are now broadly levelling off and moving onto a more even keel.
“Lots of factors can influence the complaints we see, from more people knowing about their rights when things go wrong to external factors like volatility in the stockmarket or extreme weather conditions. That’s why I believe it’s important that we continue to share our insights into complaints to help businesses to avoid the mistakes of the past.”