In what he reportedly thought was a private conversation at a fundraiser Thursday night, President Barack Obama called into question the fiscal seriousness of House Budget Committee Chairman Paul Ryan (R-WI), the author of the GOP's budget plan that dramatically cuts government spending under the guise of deficit reduction.

"When Paul Ryan says his priority is to make sure, he's just being America's accountant," Obama told his supporters at the event, according to remarks relayed on a live mic and reported by CBS News pooler Mark Knoller.

"This is the same guy that voted for two wars that were unpaid for, voted for the Bush tax cuts that were unpaid for, voted for the prescription drug bill that cost as much as my health care bill -- but wasn't paid for. So it's not on the level," Obama said.

Obama gave a nationally televised speech Wednesday laying out his misgivings about the proposal and offering a plan of his own. But the president didn't question Ryan's credentials as a deficit hawk.

Last year, Obama publicly praised Ryan's "roadmap" -- a blueprint upon which his current budget was based -- as a serious plan. "Paul, for example, head of the budget committee, has looked at the budget and has made a serious proposal," Obama said.

Ryan's ten-year proposal would cut trillions in federal spending while privatizing Medicare, slashing Medicaid, and reducing taxes on corporations and the highest income earners. He's been praised as a bold, visionary and serious thinker who's deeply concerned with the debt.

Yet the Bush tax cuts, wars in Iraq and Afghanistan, and Medicare Part D program -- all of which Ryan voted for -- have been among the most significant drivers of today's $14 trillion national debt.

Nobel Prize-winning liberal economist Paul Krugman has called the Ryan plan a "fraud," alleging that its deficit numbers are cooked and its underlying assumptions are unrealistic.

The proposal has been touted by Republicans as the most serious plan on the table to reduce the deficit in the long term. It has become a pinata for Democrats who say it leaves seniors and poor people out in the cold while giving tax breaks to the wealthy.

It's poised to pass the GOP-controlled House Friday, but it is seen as a nonstarter in the Democratic-led Senate.