Life companies accounted for 50% of the 277 complaints handled by the ombudsman between April 2015 and March 2016.
The number of complaints against the life industry increased to 139 in 2015/16, up from 114 the previous year.
Banks and life insurance companies remain the most complained about providers. However, when compared with 2014/15, the number of complaints about banks fell to 31% from 38%.
In contrast, complaints about life insurance companies increased from 43% the previous year.
Upgrades causing delays
In its annual report, the ombudsman wrote: “Several life insurance companies undertook system upgrades during 2015/16, which resulted in unacceptable delays for clients.
"This had a knock-on effect on increasing the number of complaints the providers received, particularly about delays in the claims area, which led to more delays in the complaints handing process.
“Come clients were not getting a final response within the eight-week time limit. This then led to the rise in the number of complaints and enquiries concerning life insurance companies being received by the scheme.”
Collective investment schemes
Complaints against collective investment schemes increased 10-fold, accounting for 4% of all complaints in 2015/16, up from 0.5% a year ago.
The ombudsman advised that this was primarily caused by a number of schemes being suspended for long periods, resulting in problems for clients wanting to withdraw their money.
"Many of the issues have now been crystalised because a number of the schemes are falling into liquidation."