The Prime Minister's former "family champion" Emma Harrison has announced that she is stepping down as the chairman of her welfare-to-work firm A4e.
Harrison said she was leaving as she did not want the "continuing media focus" on her to be a "distraction" for the company.
The announcement comes after she quit her role as an unpaid Downing Street adviser yesterday amid controversy over a police fraud investigation into A4e.
In a statement, Harrison said: "This has been a very tough decision for me, as I have spent my entire 25-year career building up this business and I believe so strongly in the importance of the work it does.
"But it is precisely because this work is so important that I do not want the continuing media focus on me to be any distraction for A4e, for its more than 3,500 employees, and for the tens of thousands of people across the UK and globally that look to this company to give them hope of finding employment."
A4e chief executive Andrew Dutton paid tribute to Harrison, saying that she was "devastated" to be leaving the firm.
"A4e would not exist but for the passion and ambition of Emma Harrison, who has helped improve the lives of thousands of people, and has been an inspiration to all our staff and customers for more than 25 year," he said.
Dutton said that in order to reduce "speculation and uncertainty" he had appointed the international law firm White & Case LLP to conduct an independent audit of A4e's controls and procedures.
The review will be carried out in collaboration with A4e's funders, including the Department for Work and Pensions.
"I have asked White & Case to carry out their review as quickly as possible," he said.
"It is of paramount importance to myself and the A4e board that the ongoing press speculation is laid to rest as quickly as possible, and I believe this independent review will answer the concerns raised over recent weeks."
A Downing Street spokeswoman said: "We have nothing to add to what we said yesterday."
Harrison quit as the Prime Minister's "family champion" yesterday but her departure from the unpaid role did nothing to ease pressure from the head of a Commons public spending watchdog for A4e's Government contracts to be suspended.
The arrests of four former members of staff, in January, were confirmed on Tuesday following a visit by Thames Valley Police to A4e's headquarters in Slough late last week.
Two women aged 28 and 49, and two men, aged 35 and 41, are on police bail until mid-March.
A4e said on Wednesday that the investigation was one of two outstanding cases out of nine it had referred to the DWP following internal inquiries.
The other concerned a subcontractor, it said.
A4e has been under fire for paying £11 million in dividends last year, 87% to Ms Harrison, despite all its £160-£180 million UK turnover resulting from Government welfare contracts.
Labour MP Margaret Hodge, who chairs the Commons public accounts committee, has questioned why the firm continued to get contracts despite a "dismal" past record and called for a suspension.
Despite the controversy and demands for existing work to be halted, A4e has been named as the preferred bidder for a £15 million contract with the Skills Funding Agency to provide education to prisoners in London and work advice on release, it was reported by the Daily Mail.