Specialist mortgage lender Firstmac is withdrawing from the wholesale lending market to focus on the broker market.Wholesale lending (financing the loans of mortgage managers) has been Firstmac's core business for much of its 37 years but in recent years the broker channel has become the company's biggest source of growth.Firstmac chief executive Kim Cannon said in a statement that broker sales were growing "exponentially" and "deserved a greater slice of the business's resources.""Moving away from wholesale lending will enable Firstmac to stay ahead of that evolution and refine our market focus," Cannon said.Cannon told The Adviser that the wholesale market had become highly competitive and there wasn't much margin in the business."I think the non-bank mortgage manager space has had its day unless you're doing direct retail or have some other unique market proposition. Just being in the space between the broker and the lender, there's too many mouths to feed," he said.Firstmac's loan portfolio is worth around A$7 billion.  The company also owns the online mortgage business loans.com.au.Cannon said there would not be any staff cuts as a result of the change to its business.In the meantime, Firstmac has launched an issue of residential mortgage-backed securities, seeking $500 million of funding. Firstmac Mortgage Funding Trust No.4 Series 2-2015 is backed by a pool of prime mortgages.