National Australia Bank is discounting key home buyer rates by 142 basis points in its first rates move since last week's bruising exposures about mortgage fraud at the banking royal commission.

The nation's third last lender, with about 15 per cent share of the mortgage market, is heavily discounting principal and interest, owner occupier loans to 3.69 per cent.

The new rate, which is being promoted through its branches and broker network, is a 1.42 per cent discount off the current advertised rate for the base variable rate home loan.

NAB follows-up apology to customers with big discounts for owner-occupiers Glenn Hunt

NAB relies on brokers to recommend about 42 per cent of its mortgages, compared to about 50 per cent for the other big four lenders and more than half for non-majors, according to analysis by investment bank Morgan Stanley.

It follows rate cuts by Commonwealth Bank of Australia and Westpac Group to interest-only borrowing that were readjusting their loan books after over-estimating the impact of regulatory lending caps.