(Mike Segar/Reuters)

Most of the insurance companies surveyed by the Government Accountability Office did not bill separately for the cost of abortion coverage, which is a requirement in the Affordable Care Act.

In a report released Tuesday that was commissioned by Republican lawmakers, the GAO reported that of 18 health insurance providers, 17 did not comply with that part of the law. This policy was a key reason some antiabortion Democrats agreed to sign on to the law when it was passed by Congress in 2010.

The GAO survey wasn't statistically representative of all insurance plans, so the finding can't be generalized across the country. But the insurers surveyed represented about one quarter of the qualified health plans offered in the U.S. that covered elective abortions.

In most cases, insurers estimated that the cost of covering abortion services was less than $1 a month per enrollee, but the plans are required to itemize those costs separately. According to the report, 17 providers said the cost of covering abortions were less than $1 a month, and most of those providers — all but two — said that they rounded the sum up to comply with another requirement in the law that the cost of covering the services should be no less than $1. The estimated costs ranged from as little as as 10 cents per enrollee per month to $1.10 cents per enrollee per month.

The two insurers that did itemize the costs separately labeled them as charges "for coverage of services for which member subsidies may not be used."

The provision in the law prohibits taxpayers from footing the bill for "non-excepted" abortion services (for pregnancies that are not a result of rape or incest or ones that do not threaten the life of the mother) through subsidies or tax credits. As a result, the cost of covering those services are supposed to be billed to the enrollees separately.

Antiabortion lawmakers said the report confirms their belief that the ACA illegally provides tax breaks and government subsidies to fund abortion, contrary to President Obama's assurances.

"In an 11th-hour ploy to garner a remnant of pro-life congressional Democrats absolutely needed for passage of Obamacare, the president issued an executive order on March 24, 2010, that said: ‘The Act maintains current Hyde Amendment restrictions governing abortion policy and extends those restrictions to newly created health insurance exchanges,' " said Rep. Chris Smith (R-N.J.), co-chairman of the Bipartisan Congressional Pro-Life Caucus. “It turns out that those ironclad promises made by the president himself are absolutely untrue.”

The Hyde Amendment is a law that prohibits federal funding from going to non-excepted abortion services.

The Department of Health and Human Services acknowledged that the report highlighted a need for further enforcement and clarification of the ACA rules.

“CMS will work with stakeholders, including states and issuers, so they fully understand and comply with the federal law prohibiting the use of federal funds for abortions," said HHS spokesman Ben Wakana in a statement.

The 10 states surveyed were California, Colorado, Connecticut, Georgia, Maryland, New Jersey, New York, Oregon, Texas and Washington.

The 18 insurers surveyed by the GAO provided insurance in 10 of the 28 states that allow "non-excepted" abortions to be covered by health insurance plans. The remaining 23 states all have laws that prohibit non-excepted abortions from being covered in some or all cases. There are 1,036 health plans that allow non-excepted abortions, and 1,062 health plans that do not.