WASHINGTON (AP) — House Republicans issued a report Wednesday saying that one-third of people who signed up for health insurance through new federal exchanges hadn’t paid their first month’s premium as of mid-April, which could undermine the Obama administration’s claims of robust enrollment under the new health law.

But administration officials, outside experts and even the health insurance industry immediately questioned the report, offering the latest skirmish over questionable claims and counterclaims that have come to characterize debate over President Barack Obama’s signature health law.

The report by House Energy and Commerce Committee Republicans said 67 percent of people who had signed up for health insurance through federal marketplaces had paid their first month’s premiums as of April 15. That was far lower than the numbers emerging from individual insurance companies, which have been reporting payment numbers in the range of 85 percent and above. Wellpoint reported on an earnings call Wednesday that some 90 percent of people signing up for insurance actually had paid.

Administration officials, insurers and others were quick to point out that because the GOP data cut off in mid-April, it didn’t capture a surge of health law sign-ups in March prior to the end of the first open enrollment period.

Rep. Henry Waxman, D-Calif., top Democrat on the Energy and Commerce Committee, called the report “inaccurate, irresponsible and out-of-date.”

“It is another in a long line of Republican false allegations and scare tactics about the Affordable Care Act. The law is working and providing coverage to millions of Americans, yet Republicans in Congress continue to live in a state of denial,” Waxman said.

In a statement, the committee said the administration itself has not provided figures on how many of the reported 8 million people who signed up for “Obamacare” actually paid premiums, something the administration says must come from insurers themselves. The number is important because until someone actually pays, they have not purchased insurance. Many Republicans have questioned whether the higher-than-expected sign-ups the administration has trumpeted under the health law would stand up under scrutiny.

Rep. Fred Upton, R-Mich., the Energy and Commerce chairman, said he was summoning insurers to a hearing next week to testify about Affordable Care Act enrollment.

“The Obama administration, from inside the Oval Office on down, has gone to extraordinary lengths to keep basic details of the health law from the public,” Upton said. “Tired of receiving incomplete pictures of enrollment in the health care law, we went right to the source and found that the administration’s recent declarations of success may be unfounded.”

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AP Medical Writer Carla K. Johnson in Chicago contributed to this report.