Westpac director Michael Ullmer told a parliamentary committee that the bank's board was not informed of KPMG whistleblower allegations until Labor Senator Deborah O'Neill read them out in parliament in March, despite Peter Nash, a fellow director and former KPMG partner, being warned earlier.

Ullmer said Nash did not share the allegations with other board members. Nash resigned last month after it emerged he had stayed at the home of KPMG chairman Martin Sheppard while the firm was pitching for Westpac's $25 million-a-year audit contract, a breach of tender protocols the director called a clear failure.

Westpac's general counsel did not receive a comprehensive explanation of the allegations until May 13, Ullmer told the inquiry. The director said the gradual disclosure of information about the matter had been "one of the most challenging aspects" as the board discovered the scope of the breach over time.

Former RBA governor Glenn Stevens and Optus executives are also being called before the parliamentary inquiry into KPMG's misuse of confidential client information, Colin Kruger reports for SMH business (AU).