A City Council member who helped pass the city’s new campaign finance rules is now trying to roll back a key component of the effort to crack down on political donations from lobbyists and business owners.

Council Member Peter Vallone Jr., a Democrat of Queens, said he is proposing to amend the campaign finance rules so that political candidates would no longer be required to ask contributors to disclose their relationship with the city when making a donation.

Under the rules, which began going into effect in February, donors who have business before the city are restricted to making political contributions that are only a fraction of what most citizens can contribute.

Mr. Vallone said he had been misled about a key provision of the rules, which requires candidates running for city offices to ask donors to sign legal paperwork at fund-raising events clarifying their business dealings with the city. He said the rule has a chilling effect on potential donors.

“The more we learn about this bill that we passed, the more we don’t like it,” he said. “To ask a donor to swear one way or the other over a hot dog is an outrageous requirement to place on a campaign committee.”

His amendment proposal is poised to become the latest attack on the rules, which have been called the toughest in the nation. Opponents of the legislation say it favors candidates who collect contributions from unions, which are exempt from the rules, and punish those who are supported by businesses and developers.

Earlier this year, a lawsuit was filed against the city’s Campaign Finance Board, which argued that the regulations violate the First Amendment. The plaintiffs in the suit include an owner of an asphalt corporation with a city contract, as well as the New York State Conservative Party.

Another lawmaker objecting to the new rules is Council Member Vincent Ignizio, a Republican who represents parts of Staten Island and voted against the bill. He said he thinks the proper jurisdiction for this fight is in the courts, where he said he is confident the rules would be thrown out as a limitation of free speech.

He said he isn’t opposed to Mr. Vallone’s amendment, but said any changes to the rules should correct the union exemption.

“Leaving that out would be a huge hole in any reform package going forward,” he said.

The campaign finance legislation is being implemented on a rolling basis. Registered lobbyists and donors with city contracts were the first group to have their donations capped. Next up are individuals seeking city contracts, franchises, or concessions, along with heads of organizations that are awarded city grants, and executives of banks that receive fees from the city’s pension funds. In December, real estate developers with business before the city will be required to comply with the law.

On Tuesday, when candidates for city offices are required to have reported their fund-raising figures to the city’s Campaign Finance Board, the rules will be tested for the first time.

Under the legislation, anyone with business before the city is allowed to give a maximum of $400 to a mayoral candidate or $250 to a council candidate. Other individuals can give up to $4,950 to mayoral candidates and $2,750 to council candidates.

In response to Mr. Vallone’s call to amend the rules, a spokesman for the Campaign Finance Board, Eric Friedman, wrote in an e-mail message that “when the Council voted overwhelmingly to give New York City the most comprehensive set of ‘pay-to-play’ restrictions in the nation, they included a provision in the law requiring campaigns to ask their contributors if they are doing business with city government.”

Mr. Vallone said he would withhold his amendment if Speaker Christine Quinn decided to take action on the portion of the law he has a problem with, but that appeared unlikely yesterday.

A spokesman for Ms. Quinn, Andrew Doba, said in a statement that the legislation gives average New Yorkers a greater voice in the political process and eliminates the perception of undue influence.

“These reforms were debated extensively, and the bill passed by an overwhelming majority,” he said.