Many savers may be invested in nuclear weapons, against their wishes but are completely unaware of it.
An investigation by ethical investing advocate Mindful Money showed 88 KiwiSaver providers are invested in companies making such weapons, components or delivery systems.
Mindful Money chief executive Barry Coates said the amount invested totalled more than $52 million at the end of September last year in companies, including planemakers Boeing, Airbus and Lockheed Martin, and electronics firms, including Raytheon and Bae Systems.
"Members of the public aren't given full information about what's in their KiwiSaver fund. Even if some funds say they exclude weapons, they often don't exclude all of them," Coates said.
"There is a lack of transparency... [and] this is information that the public should know."
Surveys indicate about four out of five investors do not want their money invested in weapons, fossil fuels, gambling, or anything associated with human rights abuses or animal testing.
Coates said the issue was not just direct investment in funds knowingly containing such companies, but also the investment in passive funds, which automatically track certain market indices, and offer little detail about the companies involved in such funds.
He said KiwiSaver investors could go to the group's website and find detail on the funds invested in weapons.
The information included the return on investment on funds with direct and indirect investments in weapons, as well as comprehensive information on a variety of ethical funds.
"Then they should ask their provider questions about why they are investing in such companies," Coates said.