The amount of credit extended by the main banks is up by nearly 5% compared with a year ago.
But the margin between what the banks charge borrowers and what they pay local depositors remains unchanged for the third consecutive month.
Reserve Bank figures show that loans to households, including those for the purpose of buying houses, rose 4.5% in June compared to the same month last year.
Borrowing by farmers is 15% higher than it was a year ago.
Yet the banks' average margin, which rose steadily for eight consecutive months up to March, has stayed at 2.99% for the third month in a row.
This comes as the Greens, Labour and Jim Anderton's Progressive Party prepare to kick off an inquiry into the margins charged by banks.
Offshore borrowing 'pushes up cost of funds'
In the data published by the Reserve Bank, the margin figure relates only to the cost of raising money from local deposits and not from offshore - it's the latter factor, the banks say, that pushes up the overall cost of their funds.
Recent Reserve Bank figures show that the banks raise up to 40% of their funds offshore, including from their Australian parent banks.