The House Judiciary Committee voted today to seek contempt of Congress citations against a top aide to President Bush and a former presidential aide over their refusal to cooperate in an inquiry about the firing of federal prosecutors.

"It's not a step that, as chairman, I take easily or lightly," the head of the panel, Representative John D. Conyers, Democrat of Michigan, said before the committee voted to cite Joshua B. Bolten, the president's chief of staff, and Harriet E. Miers, the former White House counsel.

Democrats have scoffed at what several of them have termed the administration's arrogant, "take it or leave it" offer. Mr. Conyers said before today's vote that members of Congress could not tolerate a situation in which "our subpoenas can be readily ignored, where a witness under a duly authorized subpoena doesn't even have to bother to show up." Mr. Bolten and Ms. Miers refused to even appear before the committee.

But there is a further complication: the White House asserted recently that the law does not permit Congress to require a United States attorney to convene a grand jury or otherwise pursue a prosecution when someone refuses on the basis of executive privilege to testify or turn over documents.