The Financial Reporting Council (FRC) has launched a probe in to Grant Thornton UK LLP, which audited Patisserie Holdings’ financial reports from 2015-17.
Grant Thornton says it will ‘fully cooperate’ with the investigation.
The accountancy watchdog says it is also examining ‘the preparation and approval’ of the bakery group’s accounts by its former chief financial officer Chris Marsh.
Marsh resigned last month and is subject to a criminal investigation by the Serious Fraud Office.
Patisserie Holdings’ 200+ site business was saved when chairman Luke Johnson invested £20m of his own money in the company. Disgruntled shareholders also approved the issuing of £15m new shares at a tense meeting earlier this month - part of which was used to repay Johnson.
The group's CEO Paul May has since resigned amid the ongoing investigation in to its accounts. He has been replaced by Stephen Francis, who previously helped turnaround meat producer Vion Food Group.
Patisserie Holdings employs around 2,500 people across five brands: Patisserie Valerie, Philpotts, Baker & Spice, Flour Power City and Druckers – Vienna Patisserie.