The market for mortgage-backed backed securities may be in the midst of its best-ever fortnight - measured by the placement of bonds with investors - with A$4.3 billion in securities sold, or planned to be sold, last week and this week.On top of the $3 billion in securities sold by Commonwealth Bank last week - and on its own a record-breaking deal - Community CPS Credit Union sold $300 million in securities (its debut as an issuer), while Liberty Financial priced $250 million in prime RMBS.Citibank is also in the market, with a $760 million sale of mortgage-backed bonds, the first foray into the Australian securitisation market by the bank since 2008.Against this backdrop, the Treasurer, Wayne Swan, publicised a directive to the Australian Office of Financial Management on Friday, which was given to the AOFM on Tuesday, asking it to invest a further $4 billion in mortgage-backed securities. The AOFM has already invested $12.7 billion in RMBS since late 2008, when Australian government support for this form of wholesale funding was first introduced, as a response to the global financial crisis.Since then, bank and non-bank funders of home loans have placed $41 billion of RMBS on the basis of Treasury data.The AOFM still has scope to invest more than $3 billion in RMBS under existing directives from the Government.This means the AOFM has $7 billion to invest, an amount the government financing agency took more than 18 months to dole out between the third quarter of 2009 and now with its recent, modest support for the CPS and Liberty deals.Under the latest directive, the AOFM is supposed to favour investment in "bullet RMBS", at least according to the announcement from the Treasurer.The operational notice published by the AOFM on Friday makes this point; though it also makes it clear that it expects issuers seeking its help to deal with any price issues within two months. Non-bank lenders connected to major banks remain ineligible to participate.