It was the government's fault, contractors on the problem-plagued website for President Barack Obama's signature health care reforms told a congressional hearing on Thursday.

In more than four hours of testimony before the House Energy and Commerce Committee, officials of companies hired to create the HealthCare.gov website cited a lack of testing on the full system and last-minute changes by the federal agency overseeing the online enrollment system.

Angry exchanges between Republicans who oppose the Affordable Care Act and Democrats defending it erupted repeatedly, while the contractors insisted their work went fine even though the software buckled when the system went online on Oct. 1.

Complaints about logging in, lengthy delays, incorrect information relayed to insurance companies and other problems have fueled continued GOP attacks on the 2010 Affordable Care Act that was upheld by the Supreme Court last year.

The White House and administration officials say the enrollment problems are being fixed. On Thursday, the Centers for Medicaid and Medicare Services (CMS) that oversees the new programs under the health care reforms said almost 700,000 applications have been submitted online on either the federal or state websites.

While the applications don't mean that many people have fully enrolled for health insurance under the new system, the figure represents a significant increase in those who have been able to start the process in recent days.

However, Julie Bataille, the CMS director of communications, was unable to say how many of the 700,000 applications were submitted on the federal website.

At Thursday's hearing, committee Chairman Rep. Fred Upton of Michigan called the launch of the website "nothing short of a disaster," noting that contractors at the hearing previously "looked us in the eye and assured us repeatedly that everything was on track, except that it wasn't."

Upton and other Republicans said it heralded problems with the rest of the health car reforms.

"I am more nervous today than I was when I got here," House Intelligence Committee Chairman Mike Rogers of Michigan said of security concerns raised by Thursday's testimony, such as code changes being made to fix the problems without undergoing normal testing.

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Health care website contractors deny culpability