At least 60,000 superannuation members with $4 billion in retirement savings – mostly customers of retail funds offered by Insignia Financial (formerly IOOF) and AMP – will be sent letters telling them their investment option failed a performance test by the prudential regulator.

“You should think about moving your money to a different super investment option or fund,” the letter, which the trustees of the funds are required by the regulator to send to members, will read.