WASHINGTON (AFP) - Just over 100,000 people enrolled in the new US Obamacare health plan in its first month, and fewer than 27,000 made it through a faulty federal sign-up website, the government said on Wednesday.

The figure of 106,185 registrations represents only 1.5 per cent of the estimated 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.

The figures were released amid a furious political row over Obamacare, with Republicans branding it a failure and the White House desperately trying to repair the federal website that was expected to process the bulk of applications under the new law.

"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.

The 106,185 figure includes nearly 80,000 people who have signed up through state based exchanges and only 26,794 people who have enrolled through the federal website, the figures showed.

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 was well below the reported half a million number that was reportedly targeted by the administration in the first month.