* Follows an anti-money laundering lawsuit from AUSTRAC
* Bank says it plans to defend itself against both lawsuits
* Class action invites holders of shares between 2015-2017 (Updates shares, adds CBA defending lawsuit in 2nd last graf)
SYDNEY, Oct 9 (Reuters) - An Australian lawfirm formally filed a class action suit against Commonwealth Bank of Australia CBA.AX on behalf of shareholders on Monday, accusing it of failing to disclose widespread breaches of anti-money-laundering rules.
The lawsuit by law firm Maurice Blackburn against the nation's biggest lender follows one by the federal agency AUSTRAC, which has accused it of more than 53,000 breaches of anti-money laundry rules - breaches which have exposed it to billions in dollars of fines.
The suit, which had been previously flagged by Maurice Blackburn and litigation financier IMF Bentham Ltd IMF.AX , said shareholders had suffered a significant share drop in the wake of AUSTRAC's accusations. law firm's statement on Monday did not specify the level of damages sought. The action invites holders of CBA shares between 2015 and 2017 to join.
CBA has not disputed that it processed tens of thousands of illicit transfers but argues the breaches were largely caused by a software glitch and contests its level of responsibility.
The bank said in a statement that it planned to vigorously defend itself against the class action suit.
The bank's stock has lost roughly 8.5 percent since AUSTRAC announced its civil lawsuit against CBA in August. CBA shares were up 0.5 percent in Monday afternoon trade, in line with the broader market.