WASHINGTON — Can the Internal Revenue Service police President Barack Obama’s health care mandate while simultaneously collecting all the taxes for running the federal government?

The question is being renewed in the wake of the Supreme Court’s decision upholding most of the 2010 Affordable Care Act as a tax issue rather than one of interstate commerce.

Nearly 2 1⁄2 years before taxpayers will have to start providing proof on their tax returns that they have health insurance, key Republicans suspect the agency already is diverting resources from collecting taxes to gear up for becoming the government’s health care cop.

“Knowing the complexity of the health law, there’s no question that the IRS is going to struggle with this,” said Rep. Charles Boustany Jr., R-La., chairman of the House Ways and Means oversight subcommittee. “The IRS wants more resources. Well, we need to start digging down into what are they doing with the resources and personnel.”

Ways and Means Committee Republicans have accused the IRS of obscuring its cost of putting in place the health care law by absorbing it into other parts of the agency’s budget. They cite a June report by the Government Accountability Office that said the IRS has not always accurately identified spending related to the new health care law.