More than two out of three people who use KiwiSaver aren't sure whether NZ Super is enough to retire on, according to the largest public survey on KiwiSaver.
The survey of 2200 people is part of Retirement Commissioner Diane Maxwell's three-yearly review of retirement income policies.
A third of people who've never signed up said they had concerns about the scheme, and three-quarters said they didn't trust the Government to leave the scheme alone.
Sixty-four percent were worried about getting their money back, while half had doubts about the providers either going out of business or not making good investment decisions on their behalf.
The most popular reason to enroll was obvious -- one in three people said they wanted to save for retirement.
This was closely followed by the appeal of the $1000 kickstart from the Government, which was withdrawn last year.
"There appears to be a problem with a lack of understanding about KiwiSaver that's putting some people off joining," says the Commission's general manager of Investor Education, David Boyle.
"The fear may be because of what occurred during the credit crisis: as finance companies collapsed investors' money in those companies was lost."
Of those who have stopped contributing, 40 percent said it was because they were no longer working and 35 percent couldn't afford to contribute.
"The worrying thing is just on 50 percent of non-members are relying on NZ Super or don't know how they are going to fund their retirement," says Mr Boyle.
The most well-known benefit of KiwiSaver was the employer contribution, which 71 percent of those surveyed were aware of.
Nearly 80 percent of active members and more than a third of non-members said the scheme should be compulsory.