Two years after the Sept. 11 attacks, Congress has done little to prepare for another calamity that could leave it paralyzed, a panel of experts said Monday.

The Continuity of Government Commission (search) was particularly critical of House leaders who are opposed to a constitutional amendment (searchto remedy the succession issue.

"It's sobering that we went up to and past the second anniversary of Sept. 11 without making any significant progress" on the succession issue, said Thomas Mann, a senior fellow at the Brookings Institution.

The commission was started after the 2001 attacks to study congressional and presidential succession in the event of a catastrophe that kills or incapacitates senior members of government.

The commission, headed by former Sen. Alan Simpson, R-Wyo., and former presidential adviser Lloyd Cutler, has backed the approval of a constitutional amendment allowing governors to appoint members of Congress in an emergency situation.

Governors already appoint senators when vacancies arise prior to an election, but House members must be replaced by a special election.

Mann said the constitutional amendment has won some support in the Senate but has met resistance in the House.

House Judiciary Committee Chairman Jim Sensenbrenner, R-Wis., and Rules Committee Chairman David Dreier, R-Calif., prefer quick elections of new members instead of allowing governors to appoint House replacements. Appointments would erode the House's status as a fully elected body, they said.

The two chairmen have proposed that elections be held within 21 days in the event that 100 or more members are killed.

But Mann said special elections can take months to stage, and state and local officials had told him that "you can't force an election like this, when the nation is in trauma, in an extraordinarily short time."

"There's a stubbornness there that I don't understand, unless there's the thought that this can never happen," Simpson said.

The commission is also taking up the issue of presidential succession (search), with focus on the constitutionality and wisdom of having the House speaker and the Senate president pro tempore being next in line if the president and the vice president are killed or incapacitated.

Among the questions is whether the Founding Fathers (search) ever intended lawmakers to be in the line of succession when they wrote in the Constitution that Congress should pick an "officer" to take over when the presidency and vice presidency are vacant.

Another issue is the propriety of having political opponents or a lawmaker from a different party take over: that could have happened had Andrew Johnson been convicted on impeachment charges or had Richard Nixon been forced to step down before he replaced Spiro Agnew as vice president.

The commission is a joint project of two Washington think tanks, the liberal Brookings Institution and the conservative American Enterprise Institute (search).