Clinton, who needs to win next week in Ohio and Texas to keep her U.S. presidential campaign alive after Obama's streak of 11 straight victories, went on the attack early in the debate at Cleveland State University in Ohio.
Obama fired back repeatedly in several testy but controlled exchanges during a debate that seemed unlikely to change the dynamic of the race before next Tuesday's contests.
The debate was sharper in tone than last week's encounter in Texas, but far less personal and angry than a Democratic debate last month in South Carolina.
Clinton kept up her recent criticism of Obama campaign literature sent to Ohio voters that she said mischaracterized her health care proposal, which includes mandates requiring Americans to purchase health insurance.
"We should have a good debate that uses accurate information, not false, misleading and discredited information, especially on something as important as whether or not we will achieve quality, affordable health care for everyone," the New York senator said.
Obama, an Illinois senator, said Clinton has frequently misrepresented his health care plan, which does not include mandates and which some critics suggest could leave 15 million Americans uninsured.
An estimated 47 million Americans - about a sixth of the population - now have no health insurance, either privately or through the government.
Clinton, once the odds-on favourite to win the Democratic nomination to contest November's presidential election against the Republican candidate, has lost big leads in public opinion polls in Ohio and Texas as Obama has gained momentum and made inroads among her supporters.
Obama said he was interested in bringing the cost of health care down and enforcing mandates could create a burden on some low-income Americans. Clinton's criticisms, he said, were part of a consistent pattern.
"Senator Clinton has ... constantly sent out negative attacks on us, e-mail, robo-calls, flyers, television ads, radio calls, and we haven't whined about it because I understand that's the nature of these campaigns," he said.
"But to suggest somehow that our mailing is somehow different from the kinds of approaches that Senator Clinton has taken throughout this campaign I think is simply not accurate."
AGGRESSIVE CLINTON
