The new enrollment data became available as Kathleen Sebelius, the secretary of health and human services, clashed again with Republicans at a hearing of the House Energy and Commerce Committee.
Ms. Sebelius acknowledged that flaws in the federal website had “dampened enthusiasm” for the health care law and had deterred many people from enrolling. But she said that “evidence of the technical improvements to HealthCare.gov can be seen in the enrollment numbers,” which she described as “very positive.”
More than a quarter-million people picked health plans last month, and more than half of them were in state-run exchanges, the administration said in a report issued Wednesday. In the federal exchange, 110,400 people chose health plans last month, four times as many as in October, when many consumers were unable to see details of health plans because of problems with the federal website.
Ms. Sebelius also announced that she had ordered an internal investigation of the botched rollout of the site.
“I have asked our inspector general, Dan Levinson, to review the development of HealthCare.gov,” Ms. Sebelius said. “We need a thorough review of the contractor performance and program management structure that resulted in the flawed launch of the website.”
It is unclear whether the inspector general will investigate the role of Ms. Sebelius or White House officials who supervised the development of the website over the last two years.
In addition, Ms. Sebelius said that the Obama administration was creating a position of chief risk officer at the Centers for Medicare and Medicaid Services, the agency that runs the health care website. The first job for the new official is to assess risks in information technology contracts, on which the agency spends more than $5 billion a year.
At the hearing, Ms. Sebelius said the federal government had made contractual commitments to spend $677 million on information technology for HealthCare.gov and had paid out $319 million through October.
However, she said that the financial management system for the federal marketplace — needed to pay insurance companies — was “in the process of being put together.” It will be ready by mid-January, she said.
The enrollment report showed that 137,200 people chose health plans through the federal exchange in October and November, the first two months of a six-month open enrollment period. The federal exchange is still lagging behind marketplaces run by 14 states, which had signed up 227,500 people through November.
Technical problems thwarted people trying to use the federal exchange in October, when 26,800 people chose a plan there. The pace picked up in November as federal officials and contractors raced to repair the website.
About 148,000 people chose health plans in the state-run exchanges last month, up from 79,400 in October, the administration said. Officials did not provide data on the ages or other characteristics of people signing up.
The new numbers do not reflect reports of a surge in sign-ups since the end of November, when the administration said the website was working well for most users. In the first week of this month, about 112,000 people selected plans through the federal marketplace, according to people familiar with the project. That means that enrollments for this month may already exceed those in November.
If sign-ups continue at the current rate, more than a million people may have selected health plans by Jan. 1, when major provisions of the new law take effect. The Obama administration was counting on having seven million by the end of the initial enrollment period on March 31.
The numbers are running behind enrollment targets developed by the administration for its own use. Federal officials were projecting that 1.2 million people would have enrolled by now through the federal and state exchanges, according to a memo prepared by the Health and Human Services Department in early September.
Even as the law provides new hope to many Americans, it is disrupting coverage for others. In recent weeks, many people have received notices saying that their private health insurance will be canceled or discontinued because it does not comply with coverage requirements of the Affordable Care Act.
“Come Jan. 1, 2014, millions more people will have lost coverage than signed up because of the health care law,” said Representative Fred Upton, Republican of Michigan and chairman of the Energy and Commerce Committee.
Many people who are eligible to participate in the federal and state exchanges have not selected health plans. Of those found eligible, 41 percent also qualified for financial assistance to help pay their premiums. That is about half of the proportion predicted by the Congressional Budget Office. The reasons for the gap are not clear.
In states using the federal exchange, the largest numbers of people signing up and selecting health plans through November were in Florida (17,900), Texas (14,000) and Pennsylvania (11,800).
Among states running their own exchanges, those with the largest numbers were California (107,100) and New York (45,500), followed by Washington (17,800), Kentucky (13,100) and Connecticut (11,600).
In addition to people who have signed up for private plans through the exchanges, Ms. Sebelius said, 803,000 people have been found eligible for Medicaid or the Children’s Health Insurance Program.