Two top Republican House lawmakers asked the Congressional Budget Office and the Joint Committee on Taxation Thursday to estimate the cost to taxpayers of Big Labor's proposed "fix" to protect its largest health care plans against Obamacare.

Big Labor leaders who want subsidies to offset the costs Obamacare will impose on union health care plans that serve workers at two or more companies met last week with top administration officials at the White House to discuss the issue.

The lawmakers -- House Education and the Workforce Committee Chairman John Kline, R-Minn., and House Ways and Means Committee Chairman Dave Camp, R-Mich. -- said taxpayers deserve to know what it would cost to give the unions what they demand.

"In the more than three years since signing Obamacare into law, President Obama has unilaterally granted waivers, special deals and delays to unions and other politically favored friends. This special treatment is unfair to the American families and individuals who are burdened with higher health costs and losing the insurance they have and like as a result of this law," Camp said.

The chairmen have requested a response from CBO and the JCT by Sept. 19.

Big Labor has been pushing the administration to bend the rules for multi-employer plans, which many unions provide for their members through nonprofit organizations.

Obamacare does not presently provide such subsidies to these plans, effectively raising their cost compared with other plans. Unions fear that will cause employers to pull out of the plans.

The present push for help is in marked contrast to the union leaders support for Obamacare prior to its passage in 2010. They were reportedly given behind-the-scenes assurances by administration officials that they would address the problem with multi-employer plans down the road. But the administration hasn't acted.

A major problem is that extending the subsidies would cause Obamacare's costs to soar. Union leaders have responded to White House delays on the issue by going public with their discontent.