MPs have written to Sir Philip Green's wife to demand answers over the "complex web" of businesses owned by the family in the wake of the BHS scandal.
Lady Green reportedly profited to the tune of many tens of millions of pounds after the sale of the high street store while employees have been left with a £571 million pension black hole.
The Business Innovation and Skills chairman Iain Wright and the Work & Pensions Committee chairman Frank Field on Tuesday made public a letter to Lady Green asking for further details about the family's businesses.
They are also demanding an explanation of Sir Philip role in their operation.
Mr Wright said: "During the hearings of our BHS inquiries, a whole array of further questions have been raised about how a big high-street name with 11,000 staff was sold for a £1 to someone with no experience of retail.
"The evidence so far points to a complex and very opaque web of privately-owned family businesses which helped make the deal possible. These complicated arrangements make it very difficult to trace where all the funds have gone.
"We are keen to follow the money and look forward to Lady Green in her capacity as owner and ultimate beneficiary of these companies writing to us to explain some of these arrangements and to set out what income her businesses have received from BHS."
Billionaire businessman Sir Philip, whose Arcadia group includes Topshop, Dorothy Perkins and Miss Selfridge, sold NHS to Dominic Chappell for just £1 last year.
Appearing before MPs last week, Sir Philip admitted he had sold the business to the "wrong guy" and apologised to staff for the collapse of the retailer, once a giant of the British high street.
He told the business and pensions committees: "Nothing is more sad than how this has ended and I hope during the morning you will hear that there was no intent on my part for anything to be like this and didn't need to be like this.
"I just want to apologise to all the BHS people who are involved in this and have been involved."
But he still faces questions about the sale of BHS and how he department store's pension deficit got so bad.