The Pensions Regulator has launched enforcement action against Sir Philip Green and other former owners of BHS.
The regulator said it was seeking redress for BHS’s 20,000 pension scheme members following an investigation.
It has sent warning notices to Sir Philip, his retail group, and Dominic Chappell, who was the owner when the department store chain collapsed.
Sir Philip said he has given the regulator "a credible and substantial proposal" for the BHS pension deficit.
The 300-page notices could see the billionaire being ordered to pay towards the shortfall, which had swollen to £571m by the time BHS went out of business.
"I have read the statement from the Pensions Regulator this evening and noted its contents," Sir Philip said.
He added that his proposal had evidence of "cash availability", could take the scheme out of the lifeboat Pension Protection Fund, and "achieve a better outcome for the BHS pensioners".
During months of talks Sir Philip has declined to publically put a number on the level of financial support he would be willing to give the scheme.
Lesley Titcomb, chief executive of the Pensions Regulator, said: "Our decision to launch enforcement action is an important milestone in our work to attain redress for the thousands of members of BHS schemes who have been placed in this position through no fault of their own."
Frank Field, who co-chaired a parliamentary inquiry into the collapse of BHS, said: "We are not surprised that the Pensions Regulator has, like all the rest of us, lost patience with Sir Philip Green’s excuses and empty promises."
Iain Wright, the other chairman of the inquiry, said that five months after Sir Philip told MPs he would "sort out the pensions mess" he has put "no credible plan or cash on the table".
MPs last month backed a call to strip Sir Philip of his knighthood, although the decision would have to be taken by the Honours Forfeiture Committee.
The Pensions Regulator opened an investigation into the BHS pension scheme in March 2015.
It said it has now launched enforcement action after reviewing almost 100,000 documents and holding talks with various BHS stakeholders.
Sir Philip and the other recipients of the notices will have an opportunity to reply.
It could then be sent to a determinations panel which may set a financial order for the regulator and former owners to agree.