By David Winning

SYDNEY--Westpac Banking Corp. said millions of breaches anti-money-laundering finance laws were caused by technology shortcomings and human mistakes, but an internal investigation had not found intentional wrongdoing by any of its staff.

Westpac has been accused by Australia's financial-intelligence agency of the biggest breach of the country's money-laundering and terrorism financing laws in history, with more than 23 million breaches that include failing to detect transfers that may have been used to facilitate child exploitation in Asia and failing to report in a timely way about $7.5 billion in international transfers.

On Thursday, Westpac laid out the results of its investigation into those compliance issues, which last year led to the departure of the company's chief executive, Brian Hartzer, and resulted in Chairman Lindsay Maxsted taking early retirement.

"We completely accept that some important aspects of Westpac's financial crime risk culture were immature and reactive, and we failed to build sufficient capacity and experience in some important areas," said Peter King, who became Westpac's chief executive in April.

Write to David Winning at david.winning@wsj.com