The country’s non-bank lenders are seizing mortgage market share at their quickest rate in nearly four years, as they take advantage of more onerous stress-testing rules that have hamstrung their larger rivals.

But brokers warn increased expectations that the Reserve Bank will increase the cash rate – and slowing economic growth – would create pain for the non-bank sector, which has largely defied a rally in other financial stocks. While Pepper Money is up nearly 20 per cent year to date at $1.48, other players like Australian Finance Group, Liberty Group and Resimac have dropped between 10 and 20 per cent, respectively.