The Financial Conduct Authority and The Prudential Regulation Authority have confirmed that they will be undertaking enforcement investigations into events at the Co-operative Bank.
The probes follow the firm's discovery of a £1.5bn capital black hole in 2013.
The bank experienced a loss of £709m in the first half of 2013, up from a £57m loss in the first half of 2012.
The firm has had a series of problems recently including pulling out of an acquisition of 632 Lloyds TSB branches in April and the departure of chief executive Barry Tootell in May.
The FCA said its investigation will look at the decisions and events up to June 2013.
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In a statement the FCA said: "The independent review announced by the Chancellor will commence once it is clear that it will not prejudice any actions that the regulators may take.
"This sequencing is necessary to ensure that the outcomes of the enforcement work are not prejudiced and follows the approach taken for both the RBS and HBOS reports."
Concerns were raised towards the end of last year in several quarters about the running of the bank. Former chairman Paul Flowers was held by Merseyside police in relation to a drugs supply investigation.
The PRA said its investigation will consider the role of former senior managers.
It said: "No further information will be provided on the investigation until the legal process has concluded and an outcome has been reached."