Westpac boss Brian Hartzer admits he spends many hours preparing for what has become a six-monthly hearing of the big four banks in front of federal MPs.
Mr Hartzer faced the House of Representatives economics committee on Wednesday, taking questions on interest rates to money laundering over a three-hour grilling.
Asked by Labor MP Madeleine King how long he takes preparing for the hearing, Mr Hartzer replied: "A lot ... probably three or four or five days."
"It's a significant impost, we are happy to do it."
The first such hearings occurred a year ago in an attempt by the Turnbull government to fend off calls by Labor, the Greens and others for a royal commission into the banking sector.
Mr Hartzer said the resources required for a royal commission would be "many multiples" of what is required for parliamentary hearings.
He said his bank has been totally transparent about issues that have been raised.
"We are getting on and taking action now to implement the reforms we need to do and I don't think a royal commission will change that," he said.