Read more: Seven numbers explaining the demise of BHS
Kate Smith, head of pensions at Aegon, said "fierce negotiations" are still to happen between the Pensions Regulator and Sir Philip Green to establish how much the PPF needs to prop up the pension scheme, and that a resolution is "a long way off".
She said: "The PPF is a place of last resort and should not be used as part of a company's de-risking or restructuring strategy.
"The Pension Regulator has "moral hazard" powers which stop employers from "orphaning their defined pension scheme and offloading it onto the PPF."
Read more: A timeline of how BHS' collapse unfolded
"Effectively, this means if they belive a company has been deliberately trying to avoid its pension obligations they can force employers to pay the debt from any part of the company - it's not just restricted to the sponsoring employer."
In a statement after Green's hearing, Iain Wright MP, chair of the Business, Innovation and Skills Committee, and Frank Field MP, chair of the Work and Pensions Committee, said they want "much more detail" on BHS' company structure - in particular, the companies owned by Green's wife, Lady Christina Green. They may also wish to know more about the dividend payments made to Lady Green.
David Buik, market commentator at Panmure Gordon, said: "I think ‘Her Ladyship’ is going to be summoned on this issue by these select committees."