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The Internal Revenue Service planted a question at an American Bar Association conference in order to reveal that it had inappropriately targeted conservative groups prior to the 2012 elections. But members of Congress are questioning why they weren't told earlier.

The question that prompted Lois Lerner, IRS director of tax exempt organizations, to apologize for the agency's actions came from Celia Roady, a prominent Washington lawyer in private practice. Roady said that she received a call from Lerner the day before the May 10 conference, requesting that Roady ask a question about tax exempt groups.

"I received a call from Lois Lerner, who told me that she wanted to address an issue after her prepared remarks at the [American Bar Association] Tax Section's Exempt Organizations Committee Meeting, and asked if I would pose a question to her after her remarks," Roady said in a statement obtained by ABC News.

"I agreed to do so, and she then gave me the question that I asked at the meeting the next day. We had no discussion thereafter on the topic of the question, nor had we spoken about any of this before I received her call. She did not tell me, and I did not know, how she would answer the question." (The event was not recorded.)

But at a House Ways and Means Committee hearing today, lawmakers questioned why Lerner had appeared before the committee just days before the conference and failed to disclose what she knew about the targeting.

"A little more than a week ago Lois Lerner was in front of our Oversight Subcommittee. She serves as the director of the Exempt Organization Division, and she has been directly involved in this matter, yet she failed to disclose what she knew to this committee, choosing instead to do so at an ABA conference two days later," Rep. Sander Levin (D-Mich.) said on Friday morning. "This is wholly unacceptable."

Acting IRS Commissioner Steven Miller was grilled by Rep. Peter Roskam (R-Ill.) over what he called the IRS's "scheme" to plant a question at the ABA but not inform Congress.

Miller said he spoke with Lerner about how to make the information in the inspector general's investigation public.

"So we were going to do it at the same time, I believe, that our intent was to talk to [Congress] at the same time," Miller said.

Asked by Roskam whether Congress was informed "at the same time," Miller said, "It did not happen, I don't believe."

In a conference call with reporters on May 10, Lerner said that she did not publicly reveal the fact that the IRS had targeted conservative groups earlier because she had never been asked.

"Somebody asked me a question today, so I answered it," Lerner said.