The House last night approved a bipartisan bill to overhaul the nation's scandal-scarred campaign finance laws by cutting off the flow of unregulated contributions to political parties and curbing attack ads by advocacy groups.

Lawmakers passed the measure, 252 to 177, as proponents overcame adamant opposition from Republican leaders.

The House action put new pressure on reluctant Senate Republicans to reverse themselves and approve a plan aimed at curbing special-interest influence on elections. As of now, the bill's supporters do not have the votes to overcome a Senate filibuster.

The final vote came shortly before midnight, after a nearly day-long debate in which House members argued, often passionately, over whether the bill would strengthen or undermine democracy and citizens' rights to free speech and honest elections.

The final margin, roughly the same as the vote by which the House approved the same bill last year, reflected lawmakers' continued concern over public reaction to fund-raising scandals in the 1996 presidential campaign and signs that spending on the 2000 race will set records. Fifty-four Republicans broke ranks with their leaders and joined most Democrats in supporting the measure.

"We're going from a government by the people, for the people, to a government of lobbyists and special interests," said House Minority Leader Richard A. Gephardt (D-Mo.) in arguing for the bill. "By passing [the bill], we will take a major first step toward restoring the American people's belief in their representative democracy and returning the agenda back to their needs."

The bill, sponsored by Reps. Christopher Shays (R-Conn.) and Martin T. Meehan (D-Mass.), would bar the use of unregulated, unlimited "soft money" from corporations, unions and wealthy individuals in federal campaigns, shutting down a fast-growing source of campaign funding that figured prominently in the 1996 campaign finance scandals.

It also would apply existing campaign rules to ads targeting specific candidates that are run by advocacy groups within 60 days of an election, which currently escape regulation because they do not call explicitly for the candidates' election or defeat. Other proposals would strengthen disclosure requirements, clarify laws governing foreign contributions to campaigns and create a commission to propose other reforms.

GOP leaders balked at rescheduling the House debate on campaign finance for this fall and fought the legislation to the end, warning wavering Republicans that they would lose their edge in soft-money contributions if the bill passed. Democrats have strongly supported the measure, though they too have come to benefit heavily from soft money.

Yesterday, both sides agreed that the system is a "mess," as Rep. John T. Doolittle (R-Calif.) put it, but they disagreed over whether the bill would make it worse or better: Worse, because it would threaten free speech and political participation, said Doolittle. Better, because it would help ensure that "elections are governed by law" and not "manipulated by loophole," argued Rep. Stephen Horn (R-Calif.)

Some of the strongest criticism of the bill came from Majority Whip Tom DeLay (R-Tex.), who said: "Make no mistake about it. Shays-Meehan guts the First Amendment, threatens citizen participation in the political process and ends the ability of citizen groups to educate the public unless they file bureaucratic paperwork with the federal government."

Supporters of the bill argued that free speech was being raised as a red herring. "This is not about freedom of speech, because we have retained free speech. It's about ending the corruption of politics," Shays said.

Before the final vote, lawmakers beat back nine proposed amendments or substitutes that would have derailed the measure by killing it outright, gutting its key provisions or destroying its base of support. The House rejected amendments to raise individual contribution limits from $1,000 to $3,000, weaken proposed restrictions on printed attack ads, require candidates to raise at least half of their contributions from their home states, exempt Internet ads from regulation, and invalidate the whole bill if any part of it was struck down by the courts.

Lawmakers also rejected three proposed substitutes that would have repealed existing contribution limits, offered narrower soft-money regulations or confined any changes to an updating of Federal Election Commission operations.

But the House voted 242 to 181 to approve, as it did last year, a proposal to prohibit foreign-born persons who are legal permanent residents but not U.S. citizens from making contributions to federal campaigns.

It also approved, 261 to 167, an amendment to require non-officeholders -- such as prospective New York Senate hopeful Hillary Rodham Clinton -- to pay the full cost of travel when they fly on government planes to campaign. At a campaign event on Long Island, Clinton called the proposal a "diversionary attempt to try to take attention away from the important issue of campaign finance reform."

Before the debate opened, President Clinton, whose controversial fund-raising practices in 1996 helped inspire the current reform effort, wrote all House members urging passage of the bill. Passage would "revitalize the political process by curbing the role of special interests, giving voters a louder voice and treating incumbents and challengers of both parties fairly," Clinton wrote.

Across the Capitol, Sens. John McCain (R-Ariz.) and Russell D. Feingold (D-Wis.) were struggling to find a way of picking up Republican support for their version of the bill without alienating Democrats, who account for the vast majority of votes in favor of the legislation.

Under an agreement worked out earlier by McCain, Feingold and Majority Leader Trent Lott (R-Miss.), the two sponsors were to submit their bill by yesterday. Yesterday, Feingold said he and McCain needed more time but would submit a bill later this week.

One option is to drop the provision on issue ads and confine the bill to curbs on soft money, thereby deflecting some of the free-speech arguments against the bill. Key Democrats have strongly objected to any major scaling back of the bill.

In two votes last year, a majority of senators voted for the McCain-Feingold bill, but it fell eight votes short of the 60 needed to cut off a GOP filibuster. No Republicans other than the seven who joined Democrats in trying to cut off the filibuster last year have said they will support the bill this year, though McCain has said at least two have expressed interest.

Staff writer Lynne Duke in New York contributed to this report.