WASHINGTON — Lawmakers are poised to trade barbs Tuesday about who deserves most of the blame for the collapse and government takeover of mortgage finance titans Fannie Mae and Freddie Mac.

The two companies, which were seized by federal regulators in September, have become highly charged political targets in the debate over what caused the U.S. housing crisis and the resulting financial fallout.

Four former top executives are scheduled to be grilled at the hearing, which is being led by Rep. Henry Waxman, D-Calif., chairman of the House Oversight and Government Reform Committee, starting at 10 a.m. EST. But there are doubts about whether the hearing will produce any solid conclusions or will just devolve into partisan bickering.

"I think we're going to get a lot of finger-pointing, which will be totally unproductive," said Bert Ely, a banking industry consultant in Alexandria, Va.

Fannie and Freddie, which own or guarantee around half the $11.5 trillion in U.S. outstanding home loan debt, long used their lobbying muscle in Washington to thwart efforts to impose tighter regulation.

Washington-based Fannie and McLean, Virginia-based Freddie are the engines behind a complex process of buying, bundling and selling mortgages as investments.

They traditionally backed the safest loans, 30-year fixed rate mortgages that required a down payment of at least 20 percent. But in recent years, they lowered their standards, matching a decline fueled by Wall Street banks that backed the now-defunct subprime lending industry.

Republicans blame Fannie and Freddie, and the effort to promote homeownership under the Clinton administration for sowing the seeds of the financial meltdown. Democrats defend the companies' role in encouraging homeownership and note that Wall Street banks — not Fannie and Freddie — led a dramatic decline in lending standards.

Both companies have been asked to turn over a long list of documents and e-mail messages concerning the risks they took in their mortgage investments, accounting, and compensation for the companies' former CEOs.

Four former CEOs of Fannie and Freddie are scheduled to testify Tuesday. One pair, Fannie Mae's Franklin Raines and Freddie Mac's Leland Brendsel, were both ousted after accounting scandals. The most recent pair of former top executives, Fannie Mae CEO Daniel Mudd and his counterpart at Freddie Mac, Richard Syron, were removed from their jobs this year after the government takeover.

Freddie Mac last month asked for an initial injection of $13.8 billion in government aid after posting a massive quarterly loss. Fannie Mae has yet to request any government aid but has warned it may need to do so.

The Bush administration and former Federal Reserve Chairman Alan Greenspan long sounded the alarm about the potential threat to the nation's financial health if the fortunes of the two mammoth companies turned sour.

In an effort to head off stricter regulations, Freddie Mac enlisted prominent Republicans to lobby on its behalf. Internal Freddie Mac budget records obtained by The Associated Press show $11.7 million was paid to 52 outside lobbyists and consultants in 2006. Power brokers such as former House Speaker Newt Gingrich and former Sen. Alfonse D'Amato of New York were recruited with six-figure contracts.

The more vexing questions will come next year, when lawmakers weigh what role, if any, the two companies play in the future.

Options include taking the companies private, morphing them into a public utility or a federal agency, or leaving them as government-sponsored entities that have private shareholders and profits, with tougher regulations.

Separately, in a report to be released Tuesday, a bipartisan commission chaired by former HUD Secretaries Henry Cisneros and Jack Kemp takes aim at the Bush administration for the foreclosure crisis. The report cites the administration's lax enforcement of fair housing laws and lackluster response for problems that have disproportionately hit poor and minority populations.

Calling the system "broken," the seven-member panel calls for the creation of an independent agency separate from the Department of Housing and Urban Development to more vigorously enforce fair housing laws.