The big banks' "house of brands" approach to the mortgage market gives them scope for plenty of variation in pricing and product features but it has not helped them hold market share over the past year.
The majors' share of AFG business fell from 76.2 per cent to 67.7 per cent in 2014.
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Westpac relies more than the other big banks on multi-branding, December 2014 data from AFG's quarterly Competition Index shows.
AFG said 8.6 per cent of its home loan sales for the month flowed to BankSA, Bank of Melbourne and St George, three of Westpac's lesser brands.
No sales are shown for Rams, a Westpac brand positioned to chase the same market as AFG.
Westpac in its own name claimed a 12.8 per cent share, giving the bank a 21.4 per cent share of AFG deal flow.
Bankwest produced one quarter of Commonwealth Bank's volumes through this channel.
NAB's flow though AFG is its NAB broker branded product. NAB's small market share of 10.2 per cent through a market leading originator may speak of a wider weakness in the market.
ANZ's share of AFG flow chopped and changed over 2014 and like all major lenders the bank ended the year with a diminished market share from its peak.
Non-major lenders increased their share of refinancing loans from 28.4 per cent in January 2014 to 41.4 per cent by December, AFG said in its index report.
"The success of non-major lenders in this category boosted their overall share of mortgages processed to an all-time high of 32.3% in December. This compares with a share of 24.0 per cent of all home loans processed in January last year."
AFG general manager of sales and operations, Mark Hewitt, said in a media release: "I am expecting the majors to hit back hard in the next quarter."
Non-majors accounted for 41.4 per cent of refinancing loans, 38.7 per cent of fixed rate loans, and 31.5 per cent of first-home buyer loans in December, AFG said.
"In an investor-driven market, major lenders still account for 73.3 per cent of all new investor loans, although this is lower share than the 80.3 per cent they held in January last year," AFG said.