Sipp complaints have risen by 37 per cent in the last year, according to the latest Financial Ombudsman Service data.
A total of 2,051 Sipp complaints were reported to the Ombudsman in the year to 31 March, up from 1,493 the previous year.
Pension transfer complaint fears are also rearing their heads again, as FOS reports an 11 per cent increase in complaints to 553, up from 496.
Pensions complaints across the financial services industry were up 2 per cent to 5,257, and complaints against IFAs about pensions were more likely than other types of cases to go in favour of the consumer, with 44 per cent upheld compared with 21 per cent for products like mortgages.
However, overall complaints against financial advisers fell by nearly a quarter over the last year, according to the FOS data.
For the year to March 2018, FOS received 1,678 complaints against financial advisers, compared to 2,197 the previous year.
Overall uphold rates in favour of the consumer for advice complaints have also ticked down from 33 per cent from 36 per cent, and annuity and drawdown complaints across financial services have remained stable.
While pensions still account for the greatest proportion of complaints against advisers, with 451 coming in during the period, payment protection insurance complaints also continued, with 56 registered against advisers.
Across all sectors, more than half of complaints were about PPI, and almost a quarter of the remaining complaints revolved around consumer credit.