ORLANDO, Fla. — Leaders of the nation’s labor unions — which some experts say benefited from the Supreme Court’s Citizens United ruling in 2010 — said on Wednesday that the ruling needed to be overturned for the good of American democracy,

Recognizing that the court is unlikely to overturn the decision, the A.F.L.-C.I.O., the nation’s main union federation, said the United States should consider a constitutional amendment to effectively overturn Citizens United, which allowed unlimited independent campaign spending by business corporations and labor unions.

Although some union leaders say organized labor will spend $400 million this year on national, state and local campaigns, many union officials are voicing fears that billionaire donors and corporations will spend huge amounts that will swamp labor’s efforts. Union leaders have been meeting in Orlando at the A.F.L.-C.I.O.’s annual winter meeting.

Asserting that the Supreme Court’s decision “seriously undermined our democracy,” the federation of 57 labor unions approved a resolution saying:

The Citizens United ruling has opened the floodgates to massive spending by corporations and even more so by wealthy donors. They are pouring money into our electoral system and threaten to drown out the voices of hard-working Americans.

The labor group said “common-sense restrictions” on this spending were needed, including disclosure of their expenditures and their contributions to “super PACs” and to politically active nonprofit groups.

To help offset the effects of the Supreme Court ruling, the union group said it supported public financing of campaigns and limits on individual contributions to campaigns. It also praised the idea of abolishing corporate “personhood” in states across the country with an eye to making it easier to limit corporations’ ability to spend or contribute corporate money to influence political campaigns.

“Business groups are not people – they are man-made creatures of law that exist to generate economic activity and create jobs and income in communities,” the A.F.L.-C.I.O.’s said. “The notion that they should enjoy the same rights and protections as natural persons is absurd and it is destructive to our democracy.”

The labor resolution was quick to add that corporations should enjoy certain constitutional protections, for instance, protections against unreasonable searches and seizures.

Efforts to reach the business-financed groups engaging in such activity were not immediately successful.

The A.F.L.-C.I.O. urged the Supreme Court and Congress to uphold the reforms it said were needed to protect American democracy from the power of money.

“As long as Citizens United remains the law of the land, constitutional change may be the only option,” the A.F.L.-C.I.O. said. “Amending the U.S. Constitution should be a rare act, done with the greatest of care,” and “narrowly crafted to protect our democracy from the economic power of the 1 percent.”

Not surprisingly, the labor unions sought to draw sharp distinctions between their political spending and corporations’ spending — they said that unions were democratic organizations run on the basis of one member one vote. “Any campaign finance reform,” the labor federation said, “needs to recognize the fundamental distinction between the democratically governed communications among working people through unions and the unaccountable spending by corporations and the rich.”