Republican senators are demanding the Obama administration rescind a “carveout” for unions in new ObamaCare regulations. 

Twenty-five GOP senators — including Minority Leader Mitch McConnell (Ky.) and Sens. Lamar Alexander (Tenn.), John Thune (S.D.) and Orrin Hatch (Utah) — signed a letter, sent Thursday, to express “deep disappointment” that the administration “has approved a final rule creating an unwarranted special carveout benefiting certain unions over other Americans.”

“We demand that the rule be immediately rescinded or we will consider using options such as the Congressional Review Act (‘CRA’) to stop the rule from going into effect,” the Republicans wrote.

The rule in question was issued March 5 by the administration and dealt with the Affordable Care Act’s “reinsurance fee.” The fee taxes health plans from 2014 to 2016 to help stabilize the individual insurance market as sick patients come on board.

Under the revised regulations, certain self-insured plans, which are used by some unions, would be excluded from having to pay the fee.

Unions have bristled at the healthcare reform law, with the AFL-CIO passing a resolution at its convention last September criticizing ObamaCare.

Republicans have seen the new rules as a gift to labor, traditionally a political ally of President Obama, but many union officials have said the new rule will do nothing to help their members.

In addition, labor and business have united behind legislation to end the reinsurance fee for all health plans.