Administration Rejects Union Pleas on Health Law WASHINGTON - The federal government on Friday rejected pleas from labor unions for a dispensation from President Obama's health care law. The decision, likely to infuriate some of Mr. Obama's closest political allies, denies federal tax credits to workers who receive health coverage under employee benefit plans sponsored by more than one employer. Such plans are common in construction and other industries. Under the 2010 health care law, the tax credits will be available starting next year to low- and moderate-income people who buy private insurance in state-based marketplaces known as exchanges. The administration's decision was made by the Treasury Department, but almost surely approved by the president. The Treasury said its conclusion resulted from a straightforward reading of the 2010 health care law, which says that workers are not eligible for premium tax credits if they have been offered affordable coverage under an employer-sponsored plan that provides minimum value. "An individual who is covered by an eligible employer-sponsored plan would not be eligible to receive a premium tax credit," the Treasury said in a letter to Congress. The Obama administration said that workers covered by multiemployer plans already received a substantial tax benefit. Their coverage is typically financed by contributions from employers, and, like most other employer-provided coverage, these contributions are not counted as taxable income to the employees, the administration said. The Treasury letter was sent Friday to Representative Dave Camp, Republican of Michigan and chairman of the Ways and Means Committee, and Senator Orrin G. Hatch of Utah, the senior Republican on the Finance Committee. They had warned the administration on Tuesday not to "provide a special exemption to unions at the expense of American taxpayers." In a joint statement on Friday night, Mr. Camp and Mr. Hatch said: "There has been far too much special treatment for politically favored friends of Obamacare. When it comes to employers and taxpayers picking up the health care tab for labor unions - it appears that is a price that is simply too high. Perhaps even this administration recognizes that there are limits to them stretching the law to reward their friends. Labor leaders criticized the health care law at a convention of the A.F.L.-C.I.O. in Los Angeles this week. They said the law could destabilize the employer-based system of health insurance and encourage some companies to dump workers into the newly created health insurance exchanges. Richard Trumka, the president of the A.F.L.-C.I.O., had conveyed those concerns directly to Mr. Obama and other White House officials. In a letter to the top Democrats in Congress in July, James P. Hoffa, president of the Teamsters, and two other union presidents said that perverse incentives in the Affordable Care Act were "already creating nightmare scenarios." They said that "numerous employers have begun to cut workers" hours" to avoid the cost of providing them health benefits. And the labor leaders said that multiemployer health plans should be eligible for tax credits, just as commercial insurance companies will be able to receive such credits to help pay premiums of low- and moderate-income people. Union leaders said they were particularly annoyed that Mr. Obama had denied their request while granting relief sought by employers. The administration delayed by one year, to 2015, a requirement for larger employers to offer coverage to full-time employees.