Superannuation funds could be forced to disclose exactly what is in at least 95 per cent of their portfolio holdings, a big jump from the current average of less than 17 per cent.

A new report by carbon-reduction activist group Market Forces released on Friday analysed the level of portfolio disclosures at the 50 largest super funds. As at June 30, 2015 these 50 funds controlled roughly $1.3 trillion, or 97 per cent of all superannuation assets not held in self-managed super funds.