Labor almost succeeded in getting up a banking royal commission last night, after the Government was caught napping when several ministers left the parliament early, perhaps forgetting their ultra slim, one-vote majority.

For a moment, the Opposition had the numbers to win several procedural votes, before enough of the absentees scrambled back just in time to stop Labor's royal commission motion from being passed into law.

It was a close call for Malcolm Turnbull, who's refused calls for a royal commission. He's promised instead to give greater powers to the corporate regulator, while the banking industry itself has proposed stricter self-regulation.

Earlier this week, the Government also instructed Small Business Ombudsman Kate Carnell to investigate banks' treatment of small business customers.