Representatives on both sides of the aisle grew heated in questioning executives of contractors that worked on the Web site for President Obama's health care law. (Sarah Parnass/The Washington Post)

Private contractors in charge of building the federal online health insurance marketplace testified Thursday that the administration went ahead with the Oct. 1 launch of despite insufficient testing.

In their first public remarks since the debut of the problem-ridden insurance exchange, executives of the main IT companies told members of the House Energy and Commerce Committee that full tests of the Web site that should have been carried out months in advance, but began just two weeks before its rollout.

“It was not our decision to go live,” said Cheryl Campbell, senior vice president of CGI Federal, which handled most of the project. She said the decision was made by the Centers for Medicare and Medicaid Services, an agency within the Department of Health and Human Services.

CMS officials declined to spell out why the complete tests started so late.

“This system just wasn’t tested enough,” Julie Bataille, director of CMS’s office of communications, acknowledged to reporters. She repeatedly cited what she called “a compressed time frame” without explaining what that meant or the reasons for it.

A look at the consumer's route through the website and the potential failure points.

“We are putting into place a much more rigorous testing process now,” Bataille said during the first of what the administration has said will be regular briefings on the progress of the Web site.

Thursday’s hearing was called by the House committee’s Republican majority, which vehemently opposes the Affordable Care Act and has brandished the Web site’s flaws as fresh evidence of the overall problems with the law.

The online marketplace is a major component of the 2010 law that is revising the nation’s health-care system. and similar state Web sites are meant to be one-stop shopping sites for health insurance for Americans who cannot get or afford coverage through a job. People who log on are supposed to be able to see an array of plans available to them at different price points and to apply for government assistance that will help most of them buy insurance.

But many who have tried to use the site have been locked out, and reports continue to emerge about errors discovered deeper in the system. Administration officials said this week they have enlisted leading experts as part of a “tech surge” to address the problems, but have declined to say when the site will be fixed.

A smoothly running site is critical, in part because most uninsured people will be required next year to carry health insurance or pay a fine.

The Department of Health and Human Services declined to send a representative to the hearing. However, Secretary Kathleen Sebelius is scheduled to testify before the panel on Wednesday. Talking with reporters Thursday, Bataille ducked questions about whether Sebelius had been aware that tests in the two weeks before the online marketplace opened showed that the Web site wasn’t entirely working.

The Washington Post reported this week that as late as Sept. 26, there had been no “end-to-end” testing of the site mimicking the real-life experience of thousands of users simultaneously trying to get online and buy coverage. During the first such test, the system crashed at a few hundred users, according to people familiar with the project.

It is unclear why there is a discrepancy between that timing and the testimony Thursday from the contractors that complete tests began in the middle of September.

Committee members asked how early that sort of testing would be done in an ideal situation.

“Months would be nice,” said Andy Slavitt, executive vice president of Optum. The company owns Columbia, Md.-based Quality Software Services Inc. (QSSI), which built part of the Web site. It also built the “data hub,” a network connecting with many other state, federal and insurer databases.

Also present at the hearing were executives from Serco, the company processing paper applications, and Equifax Workforce Solutions, a subsidiary of the credit-reporting company that is providing income and employment information to help determine a person’s eligibility for Medicaid or subsidies.

But most of the attention fell on CGI and Optum, whose representatives admitted no culpability during the hearing despite grilling by committee members upset that some of the same executives testified at a Sept. 10 hearing that their parts of the project were going well.

“Either you didn’t know about these problems or you knew about them and chose not to disclose them. Which one is it?” Chairman Fred Upton (R-Mich.) asked CGI’s Campbell.

Campbell said the parts of the project under CGI’s purview were tested properly and working well, but faulted CMS for failing to complete overall testing sooner. The agency served as the systems integrator, or coordinator, of the project.

“End-to-end testing was the responsibility of CMS,” she said.

Slavitt said QSSI sent warnings. “All of the concerns that we had, which were mostly related to testing and the inability to get as much testing as we would’ve liked, we expressed all of those concerns and risks to CMS throughout the project,” he said.

For their part, Democrats raised pointed questions about the Web site’s flaws while defending the law as a whole.

“For the Affordable Care Act to work, these problems need to be fixed and these problems need to be fixed fast,” Rep. Diana DeGette (D-Colo.) said in her opening statement.

She also took a dig at her Republican counterparts for their somewhat awkward stance at the hearing — furious about problems in the implementation of a law they oppose and argue will fail.

“I’m so happy, and touched, really, today to hear the majority express these concerns about making the ACA work better,” she said. “And I really hope that they’re legitimate in it.”

Contractors also offered updated price tags for their parts of the project. According to the executives, CGI has been paid $112 million, a sum that would likely go up to $196 million by year’s end. QSSI’s bill would be close to $85 million by year’s end. Equifax has so far collected $2 million, and Serco’s contract was for $200 million, with about $30 million already collected.