National Australia Bank is set to raise interest rates for the one group of borrowers that have so far copped less interest rate pain than most.

Street Talk can reveal that as part of a new tiered home loan pricing structure, NAB will lift rates by 0.15 of a percentage point for property investors who are paying off principal, as well as interest.

The rate rise will come into effect on April 4 and be announced to mortgage brokers on Friday, sources said.

NAB has gone further than rivals in winding back the role of sales targets for staff.

The move comes as NAB rolls out a sweeping new mortgage pricing structure that means the bank has more levers to pull when it's changing mortgage rates.

Under the new model, NAB will divide its home loan products into four distinct categories. Loans will be grouped by both borrower type (owner-occupier or investor) and loan structure (interest-only or principal and interest). It will mark the most differential pricing strategy among the Big Four in the home loan market, but it remains to be seen how it will received.