Thomas Cook's former auditor, PwC, was paid £21m for providing consultancy and non-audit work for the travel firm between 2007 and 2016, MPs have been told.
The accounting giant's head of audit, Hemione Hudson, said it also provided the travel company with advice on pay levels for executives at the same time as auditing the accounts between 2007 and 2012, earning £4m.
She told the Commons Business, Energy and Industrial Strategy (BEIS) Committee that there are now "significant restrictions" on the additional services that can be provided by a firm's auditor.
But she insisted that PwC's work in relation to Thomas Cook was "in accordance with the rules that were in place at the time".
Ms Hudson said earlier this year PwC voluntarily announced that it will phase out selling non-essential consulting services to its FTSE 350 audit clients.
"I don't think doing those non-audit services would have impacted the quality of the audit work but I do think it's very important that we do have a trusted audit profession," she said.
The UK travel company Thomas Cook ceased trading last month after failing to secure a last-ditch rescue deal, leaving an estimated 600,000 tourists stranded.