More than 50 liberal nonprofit advocacy groups have joined forces to fight a proposed exemption to a campaign-finance bill that would benefit large membership organizations like the National Rifle Association.

“It is inappropriate and inequitable to create a two-tiered system of campaign finance laws and First Amendment protections, one for the most powerful and influential and another for everyone else,” says a letter sent yesterday to House Speaker Nancy Pelosi. It was signed by groups including the Alliance for Justice, the Campaign for Community Change, the Planned Parenthood Federation of America, a variety of anti-gun-violence groups, and the Sierra Club and several other environmental organizations.

However, some good-government groups — including Common Cause, Democracy 21, and the League of Women Voters — support the bill despite the exemption as a way to achieve what they consider much-needed rules to lift the veil on the big spenders who are trying to influence elections.

The debate involves the Disclose Act, H.R. 5175, which was drawn up to counter the U.S. Supreme Court’s Citizens United ruling, which lifted many restrictions on spending by corporations or nonprofit advocacy groups on political communications. The bill, which requires such groups to reveal information about their top donors, was approved by the House Administration Committee in May.

House Democrats crafted an amendment designed to blunt opposition to the bill by the National Rifle Association. The gun-lobby group issued a statement on Tuesday saying it would no longer fight the legislation because the Democrats had agreed to exempt groups that met certain criteria — including the NRA –  from “its onerous restrictions on political speech.”

The proposed amendment would exclude from the bill’s donor-disclosure provisions 501(c)(4) organizations that have more than 1 million dues-paying members, have been in existence for more than 10 years, have members in all 50 states, and raise 15 percent or less of their funds from corporations or unions.

The letter signed by the nonprofit groups says it is unfair to release big organizations, but not small ones, from the “burdens of compliance.”

“We urge you in the strongest possible terms to work with the sponsors to remove the offending language and restore the integrity of the bill,” it says. “In its current form, we would have no choice but to oppose the passage of the Disclose Act.”

But Fred Wertheimer, president of Democracy 21, called the new language a “narrow exemption” that would benefit only “large and established c4 organizations.” He said House leaders considered it necessary to get the bill passed and that groups like the NRA would still be subject to rules requiring them to file information with federal authorities about their political spending.

“The bill continues to cover other c4 groups, including c4 groups that political operatives are using to hide the donors who are funding their campaign-related expenditures and c4 groups that serve as front groups to mask the sources of their funds.” he said.

While business interests and most Republicans have opposed the Disclose Act all along, many of the groups that signed the letter opposing the exemption support the general thrust of the bill because they want to curtail the influence of money on politics. They have expressed concern about some individual provisions, however. (See The Chronicle‘s article about the Disclose Act.)

NOTE: This article has been revised since it was originally published to clarify the views of good-government groups like the League of Women Voters.