Japanese households are rushing to private retirement products after a government report fueled fears that the national pension system won't be enough to support them during old age.

SBI Securities Co. and Monex Group Inc. have seen applications for defined contribution pension plans surge since the report was released in early June. The document, published on the Financial Services Agency's website, sparked angst after showing that a couple in their sixties may need as much as ¥20 million ($186,000) on top of their public pension to cover living expenses.

Governments around the world are grappling with how to sustain retirement systems as their populations age and interest rates plummet. The problem is most acute in Japan, where people live longer than almost anywhere else and remain averse to investing more of their $17 trillion in financial assets, despite earning virtually zero interest in bank accounts.