Sipp complaints rose 9.4 per cent in the second quarter, according to the latest data from the Financial Ombudsman Service.
The FOS received 427 Sipp enquiries between April and June this year.
The watchdog upheld 66 per cent of these.
The FOS had 390 in the same period of 2015, upholding 51 per cent.
The ombudsman also had 965 personal pensions enquiries in Q1 2016.
Thirty per cent of enquires that were taken on as cases were upheld in the period.
The regulator had 1,206 such complaints between April and June 2015, with 23 per cent upheld.
The FOS had 4,092 personal pensions enquiries in the April 2015 to March 2016 year, up 33 per cent from 3,067 in the year before.
However, the percentage of cases upheld was the same between both years at 27 per cent.
The ombudsman had 44 enquiries about income drawdown between April and June of this year, and recorded an upheld rate of 35 per cent.
By comparison the FOS had 43 complaints in the same period in 2015 and upheld 47 per cent of these.
Meanwhile the FOS had 144 consumers contacting it with complaints about annuities in the first quarter of 2016. However, the watchdog only upheld 13 per cent of these claims.
In the same period of 2015 the FOS had 265 complaints relating to annuities and upheld 20 per cent of these.