Fannie Mae and Freddie Mac, the two government-seized mortgage financiers, appear increasingly likely to pay billions of dollars to the U.S. Treasury, focusing attention in Washington on what should replace them.

Edward J. DeMarco, the acting regulator of the two companies, appeared before the House Financial Services Committee on Tuesday and urged lawmakers to reduce or eliminate the mortgage market’s reliance on taxpayers. At the same time, a Senate panel heard testimony from the authors of an alternate plan for housing-finance reform issued in February by an independent commission.

“I have been observing a developing ‘consensus’ among private-market participants that the conforming conventional mortgage market cannot operate without the American taxpayer providing the ultimate credit guarantee for most of the market,” DeMarco said at the House hearing. “That clearly is one outcome, but I do not believe it is the only outcome that can give our country a strong housing finance system. I believe that our country, and its financial system, are stronger than that.”

Washington-based Fannie Mae and Freddie Mac, based in McLean, Va., have been under U.S. conservatorship since 2008 and have drawn nearly $190 billion in taxpayer aid to stay afloat during that time. Lawmakers who don’t want the companies to return to their previous status as government-sponsored enterprises, or GSEs, are becoming concerned that political momentum for winding down and replacing them could erode as the housing market rebounds and profits soar.

“I am determined that this hearing will be the last time that Director DeMarco – or, if you believe press reports, his successor – will testify before this committee before we finally and belatedly mark up true GSE reform legislation,” House Financial Services Committee Chairman Jeb Hensarling, a Republican from Texas, said at the hearing.

One of the potential replacements for DeMarco is U.S. Rep. Mel Watt, a Charlotte Democrat who sits on the Financial Services Committee and said he intended “to listen, not to engage” in Tuesday’s hearing.

Fannie Mae, in a regulatory filing March 14, raised the possibility that it could soon be required to send as much as $62 billion to the U.S. Treasury because, once it is profitable, it may have to start counting potential tax credits as part of its net worth. The company said it would delay filing its earnings report for the quarter ended Dec. 31, 2012, while it studies the accounting issue.

Regardless of the outcome, Fannie Mae said it expects to report “significant net income” for the quarter.

The news helped send Fannie Mae’s preferred stock soaring to the highest point since September of 2008, when it was seized by the government and dividends were suspended.

The company’s common shares, which reached as high as $69.49 in 2007, more than doubled to 68 cents from 29.5 cents on March 14.

The securities may be worthless unless the companies can pay off the funds they owe to taxpayers or see their bailouts reworked. Under the current terms of the companies’ aid agreements, any money sent to Treasury is considered a return on the taxpayers’ investment, not a repayment. That’s because the federal government structured the bailout so that they could not regain independence without a new housing finance system in place.

DeMarco said he does not anticipate that legislative changes to housing finance will end the government’s involvement entirely. “What I would envision is we’ve got to start moving that dial away from government, away from taxpayers, and back toward a more private capital participation,” he said.