Only 106,000 people enrolled in the new US health plan in its first month and only a quarter did so on a faulty government website, in early failures for President Barack Obama's top domestic achievement.
Government figures published Wednesday were the first official snapshot of the progress of "Obamacare" which has been plagued by glitches since it debuted on October 1.
The data fueled fresh and fiery debate in Washington over the new law, with Republicans saying it proved the reform—the closest America has ever got to universal health coverage—was a failure and should be scrapped.
The figure of 106,185 registrations represents only 1.5 percent of the targeted total sign-up for the plan by the end of the enrollment period at the end of March, the Health and Human Services Department said.
Officials had targeted an initial enrollment of around half a million people in the first month—but it is clear the badly flawed federal government website is inflicting serious damage on the law's high stakes rollout.
"We can reasonably expect these numbers will grow substantially over the next five months," said Health and Human Services Secretary Kathleen Sebelius.
The site, Healthcare.gov, is "getting better, it is getting better every day," she added.
Nearly 80,000 people who signed up did so through online health insurance exchanges set up in 14 states and Washington DC.
Only 26,794 people enrolled through the faulty federal website, which is expected to handle most enrollments and those from states that are not setting up their own exchanges, the figures showed.
The White House says technical experts are working around the clock to fix the website, following complaints that it freezes users out, logs them off or is simply impossible to navigate.
Enrollment was always expected to be slow in the first month of Obamacare as customers shopped around for plans and lacked urgency given the final deadline for signing up is at the end of March.
But the October figure shows the White House has substantial catching up to do if it is to meet its targets for the end of the enrollment period.
Officials said the figures included people who had bought plans and those who were yet to pay a premium.
They declined to provide a breakdown of the ages of those signing up—the system relies on a high take up from young, healthy Americans, to compensate for the higher costs expected to be run up by older, sicker patients.
The new health care law is designed to offer insurance to millions of Americans who have never been able to secure it before—some because of pre-existing health conditions like heart disease that insurers were unwilling to cover.
But the website debacle has played into the hands of Republicans who say the federal government has no business intervening in the private health care market and and should not be dictating health choices to Americans.
The launch has also been damaged by the spectacle of millions of Americans receiving notices from insurers telling them that they will lose health policies they already have because of Obamacare.
Obama repeatedly told Americans that if they liked their health insurance, they could keep it, and was last week forced to apologize as Republicans claimed he had been dishonest.
The White House says the insurance plans were cancelled because they did not meet stringent standards required by Obamacare, and that Americans now have access to much better healthcare coverage.
But Republicans, who have opposed the law all along, warn that many people will end up paying more for their coverage.
"This report is a symbol of the failure of the president's health care law. It is a rolling calamity that must be scrapped," said Republican House Speaker John Boehner.
Republican Senator Marco Rubio said that the "abysmal Obamacare enrollment numbers are another early warning sign that this legislation is deeply flawed and ultimately cannot be fixed.
"Only full repeal and replacement can begin undoing the damage."