The gap between real mortgage rates and those banks are using to test customers is widening.
Banks are testing borrowers at servicing rates of more than 7%, despite two-year mortgages dropping to 2.65% in recent weeks.
According to advisers, servicing rates greater than 7% are commonplace among major banks, with ANZ testing borrowers' ability to repay loans at a lower rate of 6.65%.
While Reserve Bank pressure has forced home loan rates down, advisers fear clients will not pass the harsh servicing test rates.
David Green of adviceHQ said: "The gap between market rates and servicing rates continues to grow – a balancing act between growth, risk and responsible lending."
Glen McLeod of Edge Mortgages said banks have not shown the "enthusiasm that the Reserve Bank probably would’ve liked to have seen". He added: "At this point, the banks seem to be more worried about serviceability."
McLeod hopes banks might "change their tune" as the economic picture becomes clearer.
"The banks are definitely toeing the responsible lender code line at the present time. But at some stage they will need to open up lending in order to make a profit, it is a balancing act," he added.
Advisers say the main banks are still testing investors on a principal and interest basis, as well as using the high test rates.
Stephen Wilton of The Advice Group called for a lower test rate and a rethink from borrowers: "What's wrong with residential debt being serviced at 6.5% on principal and interest, and investment debt at 6.5% on interest-only?"