Anglo Irish Bank is taking legal action against its former auditor Ernst & Young for failing to spot the bank's massive exposure to the Irish property bubble.
Ernst & Young said it would "vigorously defend" itself.
The bank, which is based in the Republic of Ireland, said it filed the action against Ernst & Young on Tuesday, in proceedings that "relate to the role of Ernst & Young as auditors to Anglo Irish Bank Plc pre-nationalisation".
The BBC reports Ernst & Young audited the bank's books in the years leading up to the financial crisis and the 2009 nationalisation, which .
The bank's affairs were taken over by the Irish Bank Resolution Corporation in 2009, at a cost of more than £20 billion to Irish taxpayers.