The Financial Ombudsman Service upheld almost double the proportion of complaints against banks as it upheld against larger advice firms in the second half of last year.
FOS complaints data, published this week, lists firms that have had 30 new and 30 resolved complaints between July 1 and December 31.
It shows that an average of 81 per cent of complaints were upheld across the top six banks.
For the six adviser firms included in the data, the average uphold rate was 44 per cent.
Royal Bank of Scotland had the highest uphold rate of all the banks, with 93 per cent of complaints upheld.
RBS generated a total of 6,533 FOS complaints between July and December, of which 2,737 complaints were against RBS subsidiary NatWest. The FOS upheld 85 per cent of NatWest complaints.
Lloyds Banking Group had the most complaints referred to the FOS, with 20,310 complaints. The FOS upheld 87 per cent against Lloyds TSB.
Between July and December, Barclays had 12,273 complaints, Santander had 6,202 and HSBC had 6,190.
The FOS upheld 84 per cent of cases against Barclays, 55 per cent against Santander and 80 per cent against HSBC.
Of the advisers, AWD Chase de Vere got 38 complaints and the FOS upheld 81 per cent. Aegon-owned Positive Solutions got 60 complaints and 70 per cent were upheld.
The FOS received 140 complaints against Sesame, 50 against St James’s Place, 47 against Personal Touch Financial Services and 116 against Openwork.
It upheld 36 per cent of complaints against Sesame, 27 per cent against St James’s Place, 26 per cent against PTFS and 25 per cent against Openwork.
AWD head of communications Patrick Connolly says: “The reason for the uphold rate is that complaints relate overwhelmingly to legacy sales issues.”