Rep. Henry Waxman (Calif.), the top Energy and Commerce Democrat, accused Republicans of manufacturing "deeply flawed studies" projecting premium increases under the law.
"The vast majority of Americans will see their premiums stay stable or dramatically decrease in 2014," Waxman said. "For the overwhelming majority of Americans, health reform will result in much more affordable coverage."
Republicans charged Obama and his supporters with setting unreasonable expectations that will not be met by healthcare reform.
"Making low-income and everyday Americans pay more for private health coverage is not health reform. It's making their life harder at a time when our fellow citizens face sluggish economic growth, slow job creation and little disposable income," said the subcommittee's top Republican, Rep. Joe Pitts (Pa.).
Many Republicans have cited a study by Oliver Wyman, the management consulting firm, predicting some premium increases under the law.
Christopher Carlson, an official with the firm, said Friday he expects that "most people will see a decrease in the amount of premiums they pay" as a result of the law's subsidies to purchase insurance.
The other witnesses included former Congressional Budget Office director Douglas Holtz-Eakin, who predicted a rise in premiums, and Wendell Potter, an insurance executive turned whistleblower who now works for the Center for Public Integrity.