Speaking Friday at the National Housing Conference Annual Policy Symposium, Mary Miller, the Department of the Treasury’s under secretary for domestic finance, said that recapitalizing Fannie Mae and Freddie Mac “adequately” would take “at least 20 years.”

In her prepared remarks, Miller said that the American taxpayers should not be at risk if the housing market crashes again. “Even if truly rehabilitating the GSEs were possible, recapitalizing them adequately would take at least twenty years,” Miller said. “During these 20 years, the taxpayer would remain at risk of having to bailout the GSEs during another downturn. We would also be signing up for another 20 years of underserving responsible credit-worthy Americans seeking to buy a home.”

Miller said that the current design of the housing market is deeply flawed. “We need to address the underlying cause, an unsound business model where the majority of housing credit is backstopped by the taxpayer,” she said. “The fundamental misalignment of incentives at the GSEs, where private gains were made possible through the public’s risk of loss, helped exacerbate the crisis.”

Miller called the current system “unacceptable” and called for change. “This status quo, where Americans bear a significant amount of the risk in the housing market in exchange for a system that does not serve all credit-worthy borrowers, is not acceptable,” Miller said. “We must create a new housing finance system that better serves the needs of American taxpayers, borrowers, and renters.”

Miller said that the administration remains committed to reforming the housing finance system because it is the “last big piece of unfinished business left from the financial crisis.”

In her speech, Miller reiterated the administration’s position that the GSEs need to be wound down. “There is no quick fix solution around this,” Miller said. “Only legislation can protect taxpayers by responsibly winding down the GSEs and replacing them with a system where a government guarantee is transparent and explicitly priced.”

Miller said that critics of the plan to wind down the GSEs often cite the recent profits returned by the enterprises. “Opponents of reform usually fail to mention that the GSEs’ profits for the last two years have consisted largely of tax-related one-off gains and legal settlements,” she said.

“Their profitability has also been driven by income from their retained portfolios, which benefit from being funded through Treasury capital support at low rates the private market cannot obtain,” she continued. “The GSEs will not be able to replicate the levels of revenue they achieved over the past two years. In short, adequately recapitalizing the GSEs would take longer than many realize or would admit.”

Miller said the current state of the GSEs is keeping credit away from potential borrowers. “The uncertain future of the GSEs contributed to lenders’ reluctance to serve all credit-worthy borrowers, and this has effectively shut many Americans out of the purchase market,” she said.

Miller praised recent announcements from the Federal Housing Finance Agency and the Department of Housing and Urban Development that aim to relax the current tight standards. But she said that those programs would not be enough to solve the problem. More has to be done, she said.

“Allowing FHA risk sharing loans to be securitized by Ginnie Mae would help provide state and local housing finance agencies with the low-cost capital they need to provide affordable mortgages and rental units in the communities they serve,” she said. “However, we need legislation to give Ginnie Mae this authority. This has been an Administration priority since 2013, and we urge Congress to act.”

Miller said that in the meantime, the Treasury is “exploring options” to provide assistance to HFAs. “We are working with HUD to see if any existing sources of federal funding may be available for loans already guaranteed through FHA’s Risk Sharing program,” she said. “This could present a viable interim solution and we hope to say more in the near future.”

Miller also spoke of the ongoing rental affordability crisis, which has been one of the touchstones of the administration’s recent messaging. “The crisis also made it significantly harder to find affordable rental units as the demand for rentals has increased, while at the same time new affordable multifamily rental properties have become more difficult to finance,” she said.

Miller said that while there has been some home price recovery, there hasn’t been enough yet. “The ongoing recovery has helped reduce the number of underwater borrowers by nearly half over the past three years, from over a quarter of all borrowers in 2010 to slightly less than 13% of borrowers last year,” she said. “The share of severely underwater borrowers, those that have mortgages that exceed property value by more than 125%, has fallen even more dramatically, from over 11% in 2010 to less than 5% today.”

Miller said that much of the home price recovery has been due to investors, who are capitalizing on the REO-to-rental market at a time when rental properties are much needed. “Investors have purchased and rehabilitated many of these properties and turned them into rental housing,” she said. “Getting that inventory back into circulation is unequivocally good.”

Whatever the recovery may yet be, it appears that Miller may not be a part of it for much longer, at least not in her current role. According to reports, Miller is set to resign her position at Treasury, effective in early September. The Wall Street Journal reported Thursday that Miller’s departure was announced internally earlier on Thursday.

In the interim, Miller assured her audience that she and the rest of the administration are working to “define” the future of housing in the U.S. “Those of us who are working on reform no longer ask whether there should be a government role in the housing market, we are defining it,” she said. “We are no longer debating the merits of countercyclical authority so the government can help mitigate a downturn; we are working on determining the best tools and triggers for that intervention.”