Two congressmen on Thursday demanded the resignation of a top Obamacare official who twice testified under oath that was “on schedule and on track” despite being told beforehand by government consultants that the project was headed for disaster.

During an often-heated hearing, members of the House Energy and Commerce Committee's Subcommittee on Oversight and Investigations repeatedly challenged the credibility of Gary Cohen, one of the senior federal executives overseeing the development and launch of

Cohen is director of the Center for Consumer Information and Insurance Oversight, a division of the Centers for Medicare and Medicaid Services in the Department of Health and Human Services.

Rep. Michael Burgess, R-Texas, a physician and vice chairman of the subcommittee, told Cohen, “If I was [HHS Secretary Kathleen Sebelius], I would fire you. That would have happened in October.”

Rep. Marsha Blackburn, a Tennessee Republican on the subcommittee, agreed, saying, “Mr. Cohen, I agree with Dr. Burgess. You ought to be fired.”

Cohen delivered glowing testimony to the subcommittee twice last year about the progress being made on the website, on April 24 and Sept. 19.

During the April testimony, Cohen said he was "optimistic and confident where we are at this point” in development of

Lawmakers did not then know that Cohen had received two devastating briefings about the state of the website just days before delivering that testimony.

Those briefings came from executives with consultant McKinsey & Co., who warned that the website was far behind schedule. They also pointed to 13 risks that could lead to overall “system failure.”

Rep. Fred Upton, R-Mich., chairman of the energy and commerce panel, also confronted Cohen about his previous testimony during Thursday's hearing.

“During more than four hours of your testimony, there was no mention of the fact that you had been briefed twice by McKinsey in April of last year and warned of the risks facing the marketplace’s website, ” Upton said.

Notably absent from the hearing was Rep. Henry Waxman of California, the ranking minority member of the Upton panel and an outspoken defender of the Obamacare program.

In Waxman's absence, Rep. Diana DeGette, D-Colo., the senior Democrat on the subcommittee, ridiculed Cohen's Republican inquisitors, saying “let’s not sit around griping about what happened admittedly last year.”

Rep. Tim Murphy began the hearing telling Cohen that “it seems like you’re faced with two alternatives today.” Murphy is the subcommittee's chairman.

"Either you didn’t know about the problems with when you testified last year, or you did and you decided not to inform Congress.,” Murphy said.

Burgess also asked Cohen if he wanted to change any of his previous testimony regarding

“Knowing what you know now, would you like to revise that [earlier] answer in any way?” Burgess asked.

“Clearly I was wrong,” Cohen replied, but said his staff misled him.

“I was very careful to get a thorough briefing from the people who were responsible for overseeing the website, and the answer I gave you was exactly what they told us our functionality would be on October 1,” Cohen said.

“Why should we believe you now when nothing you have said over the past year, year and a half, has been accurate?" Burgess asked.

Cohen replied, “Because the site is working, Congressman.”

“I submit to you that it is not working because it the back end paperwork is not flowing, subsidies are not flowing,” Burgess shot back. “This thing is a disaster.”