It's "inconceivable" that President Obama was unaware that the Internal Revenue Service was targeting conservative groups, House Speaker John Boehner said today.

"It would be inconceivable in my operation that my staff would know it and I wouldn't," the Ohio Republican told ABC News' George Stephanopoulos on "Good Morning America."

"It just doesn't pass the straight-face test. How could - how can your chief of staff - your general counsel know, and you not know?"

Obama has said that he first found out about the outcome of an inspector general audit when the report was released publicly, but his aides say they were informed that a report was forthcoming weeks earlier.

Boehner said the White House has "stonewalled" requests for additional information to aid congressional investigators. And though he does not believe that the directives to target conservative groups for heightened scrutiny came from "some low-level employees in Cincinnati," Boehner would not say whether he believes Cincinnati employees were directed by the White House.

"I don't know where it was directed from," Boehner said. "Our committees are going to do their job. Under the constitution, we're required to provide oversight in the executive branch.

"We've got an important job to do here, and we're going to do it."

(ABC News)