Lawyers are launching Australia's largest shareholder class action against the Commonwealth Bank.

Maurice Blackburn Lawyers and litigation funder IMF Bentham are trying to get a case up against CBA over its alleged 53,000 breaches of anti-money laundering and counter-terrorism financing laws.

CBA knew about flaws that left it in breach of the law back in 2015, but took two years to tell the stock exchange, the legal firm says.

“AUSTRAC alleges money was laundered and people with terrorist links engaged in suspicious activity through the CBA's accounts,” Maurice Blackburn's national head of class actions Andrew Watson said this week.

“To rub salt into that wound, it now appears the CBA completely failed to honour its obligations of transparency and openness to shareholders.”

CBA has admitted its board found out about a coding error with its intelligent deposit machines around the time it had been fixed in late 2015.

Mr Watson said the bank - Australia's largest listed company - did not tell the share market for nearly two years.

“The AUSTRAC allegations are extensive and it is astounding that the market would not be advised of such serious and repeated breaches as soon as the company became aware of them,” he said.

AUSTRAC has accused CBA of systemic failure to comply, leading to over 53,700 breaches of anti-money laundering and counter-terrorism financing laws.

The class action is expected to cover only those who bought shares during the near two-year period before AUSTRAC’s revelations on August 3 this year, which Mr Watson says still amounts to thousands upon thousands of shareholders.

“I'd anticipate that we will have very large levels of interest from institutions and retail shareholders,” he said.

“On any view it's going to be a very large claim.”

CBA says it has yet to be served with any legal proceedings, and that it will keep the market informed of developments.

Experts have weighed in on the looming legal endeavour, and suggested the most likely outcome will be some sort of settlement to avoid a lengthy and damaging trial.