ASB Bank's profit has dropped almost 11% in the half year to the end of December.
The bank reports it made $238 million, after including a $41 million accounting loss due to new international accounting standards.
ASB Bank chief executive Charles Pink says lending margins are under pressure and the bank has had to make more provisions for stressed loans.
He says the profit fall would still compare favourably with many banks globally.
Credit card interest rates lowered
ANZ and the National Bank have cut their credit card interest rates .
ANZ will lower interest rates across all its cards by one percentage point, following a 1.25 percentage point cut last month.
That brings its rates to between 13.9% and 19.95%.
The National Bank will lower rates by between one and 1.2 percentage points following similar cuts last month.
The new rates will take effect in March.