The nation's new campaign finance law discriminates against low-income Americans because it doubles the amount that individuals can give a candidate, therefore rendering small donations ineffective, lawyers told a panel of federal judges in Washington yesterday.

On the second and final day of hearings on the McCain-Feingold campaign finance bill, lawyers for a group of low-income plaintiffs and the U.S. Public Interest Research Group told the three-judge panel that by allowing individuals to donate as much as $2,000 to a presidential or congressional candidate, the new law effectively disenfranchises the poor.

The limits apply to so-called hard money, which the national political parties still can raise and spend. The law, which took effect a month ago, bars the national parties from raising "soft money," the unlimited contributions from corporations, interest groups and others.

"Under the hard money increases . . . bundling [contributions] from the well-connected will grow to be intolerable," said the group's lawyer, John C. Bonifaz. "The First Amendment isn't the only issue at stake here. There's also equal protection, and that must include equal protection of the poor."

As evidence, Bonifaz cited a study concluding that one-tenth of 1 percent of the voting age population made contributions of $1,000 or more in the 1999-2000 election cycle. Yet those funds accounted for about half of the total donated by individuals.

He said that wealthy, corporate donors often "bundle" such donations by canvassing business associates, friends and family members to put together huge contributions.

Under the new law, a bundle of $2,000 hard-money donations would overwhelm the $10 and $20 donations that low-income voters can afford, said Stephanie L. Wilson, executive director of the Fannie Lou Hamer Project, a voting rights group named after a Mississippi civil rights activist.

"I'm a single parent with three kids, worried about health care and day care," Wilson said. "But I should still be able to meaningfully participate in the electoral system. Under the new law, I think my $10 donation would buy me absolutely nothing."

The three-judge panel is composed of Karen L. Henderson of the U.S. Court of Appeals for the D.C. Circuit and U.S. District Judges Colleen Kollar-Kotelly and Richard J. Leon. Henderson hinted Wednesday that the panel may render a decision by late January. From there, the case is expected to move immediately on appeal to the Supreme Court.

Henderson said at the close of the hearing that the panel would unseal all documents in the case in the coming weeks unless lawyers could convince the court that the information should remain private.