House GOP pounces after Obama budget director says health mandate ‘not a tax’

House Republicans quickly pounced Wednesday after the White House's top budget official said the healthcare reform law's penalty on people who don't buy insurance isn't a tax.

Republicans argue the admission from Acting White House Budget Director Jeff Zients undermines the White House's defense of the law before the Supreme Court. Congress has broad power to impose taxes.

"That's not a tax?" Rep. Scott GarrettScott Garrett10 races Democrats must win to take the House ‘Crystal Ball’ favors GOP in race for House Could the House really flip? MORE (R-N.J.) asked in reference to the mandate.

"No," Zients answered, "that's not a tax."

"I just wanted to be clear on that because that's not the argument the administration is making before the Supreme Court," said Garrett.

Other Republicans immediately highlighted the exchange.

"The President’s budget director contradicts the President’s #SCOTUS case on constitutionality of his health care: law," the press office for Rep. Paul RyanPaul RyanPoll: GOP has edge for open Wis. House seat In six new sanctuary states, Americans put at risk What the 'Bernie Sanders wing of the GOP' can teach Congress MORE (R-Wis.) tweeted after the exchange.

In reality, the White House's legal argument is more complicated.

The administration has argued that the penalty isn't per se a tax — that would violate the president's pledge not to raise taxes on the middle class — but that the authority to impose it is derived from Congress's authority to raise taxes. The health law calls for the mandate and the penalty to start in 2014.

In filings before the Supreme Court, White House lawyers have adopted two seemingly contradictory stances, The Hill reported last year: the administration wants an immediate ruling, so it argues that the penalty shouldn't be considered a tax because federal law prescribes courts from blocking taxes before they go into effect.

When it comes to the merits of the penalty, however, the administration has argued that it is a tax.

—Erik Wasson contributed to this story.