But while Secretary of Health and Human Services Kathleen Sebelius regretted that navigating HealthCare.Gov has been a "miserably frustrating experience" for many, she insisted that so-called "Obamacare" has been working well for millions of Americans.
The pointwoman for the new health care law sounded chastened about the trouble-plagued online portal through which millions are expected to register for health insurance.
"Let me say directly to these Americans: You deserve better. I apologise. I'm accountable to you for fixing these problems," Sebelius, the seniormost administration official to testify before Congress on the health care law, told a closely-watched House panel.
"Hold me accountable for the debacle. I'm responsible," she said.
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HealthCare.Gov, which allows access to exchange marketplaces where Americans can purchase private insurance, debuted on October 1.
Committee chairman Fred Upton said he has seen little improvement in the website's performance since then, noting that his staff was "hit with an error message" even as they tried to go on the page today.
"After more than three years to prepare, malfunctions have become the norm."
Sebelius's appearance marked the third congressional hearing in a week addressing the faulty start to Obamacare.
Critics like Blackburn have focused on how the health care law is booting millions of people off their plans, but Sebelius countered that insurance companies routinely alter coverage in the individual market, and that people on these plans often hold them for less than a year.
And skeleton policies that do not measure up to Obamacare's rules, including not providing free mammograms or charging women 50 per cent more than men, will need to be changed to conform to the law.