White House spokesman Jay Carney grew testy Wednesday in defending the Obama administration’s decision to delay the implementation of the health care law’s employer mandate, saying critics who question the legality of putting off parts of the law are “willfully ignorant.”

Republicans and at least one Democrat — Sen. Tom Harkin of Iowa — are questioning whether the administration has the legal authority to delay the part of the law after the Treasury Department last week announced it was putting off for one year the requirement that businesses with more than 50 employees provide insurance.

But Carney brushed off those questions as disingenuous — aimed only at undermining the entire health care law.

“People who suggest that there’s anything unusual about the delaying of a deadline in the implementation of a complex and comprehensive law are deliberately sticking their heads in the sand or are just willfully ignorant about past precedent,” Carney told reporters during Wednesday’s daily briefing.

When reporters asked whether he was lumping Harkin, who played a key role in crafting the bill as chairman of the Health, Education, Labor and Pensions Committee, into that group, Carney brushed that question aside saying only that the White House would talk to Harkin.

After reporters continued to pepper him with questions about Harkin, Mr. Carney dismissed them outright as cover for Republican attempts to dismantle the law.

“You can pretend this is about Tom Harkin, but you know it’s not,” he said.