WASHINGTON — President Barack Obama on Sunday defended the transparency of his signature health care law, after one of the White House’s advisers on the reform said the law passed, in part, because of the “stupidity” of American voters.

Obama said the law, which extends private health coverage to uninsured Americans, was extensively analyzed and written about before its passage in 2010, and in subsequent debates.

“The fact that some adviser who never worked on our staff expressed an opinion that I completely disagree with … is no reflection on the actual process that was run,” Obama said during a press conference at the Group of 20 leaders meeting in Brisbane, Australia.

“I would just advise every press outlet here, go back and pull up every clip, every story … It was a tough debate.”

Obama was responding to the comments of Jonathan Gruber, a health economist at the Massachusetts Institute of Technology who advised the White House on the Affordable Care Act as well as Massachusetts on the health law enacted by former presidential candidate Mitt Romney when he was governor of that state.

In several speeches from prior years that came to attention in the past week, Gruber said the law’s ultimate passage benefited from the “stupidity” of American voters, who did not fully understand the provisions.

Gruber’s comments were quickly picked up by Republicans in Congress, who are committed to repealing or dismantling parts of the health care law.

But the White House trumpeted some good news about the health reforms this weekend, saying 100,000 people were able to submit new online applications for health coverage during the start of open enrollment on Saturday.

The HealthCare.gov website was beset by technical glitches last year that shut down the operation within minutes of its opening and drove Obama’s signature domestic policy to the brink of disaster.

The administration expects 9.1 million people in total to enroll in government-backed federal and state health insurance marketplaces this year, down from an initial target of 13 million.

“When you give the American people the tools to make the right choices for themselves, they’re going to do that,” Health Secretary Sylvia Mathews Burwell said of the enrollment figures on NBC’s “Meet the Press.”

“And that’s what this is about.”