Australian Prudential Regulation Authority chairman John Laker may not widen the definition of liquid assets to include mortgage-backed securities, as some in the industry hope."The discretion to add additional assets is qualified by the fact that these assets… must have a proven record of a reliable source of liquidity in markets even during stressed market conditions," Laker told a Senate estimates hearing on Thursday."So, the discretion is carefully qualified by the fact that these assets need to demonstrate liquidity in duress."According to a report in the Australian Financial Review, Laker said that in deciding if more assets beyond Commonwealth government and semi-government bonds would qualify APRA would look at other assets' performance during a crisis.