Twenty bankers from National Australia Bank have been sacked or have left the lender for breaching its policies when issuing 2300 home loans, including some that may be based on false information.

NAB on Thursday said it had also disciplined a further 32 staff for failing to follow its strict policies when writing the loans, which mainly went to foreign buyers of Australian property.

In the latest example of misbehaviour in the banking industry, NAB said that in 2015 it became aware of the problematic mortgages, many of which were sold via "introducers" – people outside the bank who collect a fee for referring a customer.

NAB said some of the loans may have been submitted without accurate information about the customers, which could include incorrect documents such as payslips.