Much of the talk surrounding the General Motors bankruptcy has focused on the plight of bond holders.

But taxpayers are the most at risk, says bankruptcy expert Edward Altman, a business professor at New York University.

"The bill is now up to $50 billion or more, which is what we said would be needed, but the government should be first in line" among creditors, he told Bloomberg TV.

"The government will now have stock in the company, more than 72 percent. It is a big uncertainty if the company will do well."

Bottom line: "The potential biggest loser, unfortunately, is the U.S. taxpayer," Altman says.

The government already has extended $19.4 billion of loans to GM and is expected to provide another $50 billion in GM's reorganization.

The Treasury is slated to receive 72.5 percent of GM's equity. GM plans to turn more than $50 billion of Treasury debt into common and preferred stock and warrants.

Altman says bankruptcy reorganization won't solve all of GM's problems.

"There are a disturbing number of Chapter 22s, where they have to file again within five years because it did not work, and they either have too much debt or haven't fixed the operational problems," he says.

Others are more optimistic. "If they take out all that cost and capacity, what they're teeing up potentially is an era of unprecedented profitability," David Cole, chairman of the Center for Automotive Research, told The Wall Street Journal.