House leaders on Thursday defended their effort to require certain advocacy groups to reveal their donors amid criticism from those groups that the provision threatened their freedom of speech.

The statement came as negotiators from the House and Senate seek a deal on Senate Bill 127, which was originally designed to allow local officials to escape state ethics commission fines. The House, however, earlier added language that could discourage third-party groups such as Americans for Tax Reform from launching campaign attacks.

The bill would require issue advocacy organizations that get involved in elections in Georgia to file disclosures saying how much they spent on the effort and where they got their money. It’s lead dozens of organizations, including tea party groups, Washington-based think tanks and others to call the bill an infringement on the First Amendment.

Not so, one House leader said.

“Senate conferees are pushing back on the House proposal which would simply require advocacy groups to disclose their donors and expenditures over $100 — exactly as candidates must do,” one House official with direct knowledge of the negotiations who was not authorized to speak on the record told The Atlanta Journal-Constitution. “The Senate seems to be bowing to some fringe groups who wish to hide their activities from the light of public scrutiny.”

A coalition of more than a dozen groups wrote to conferees and Gov. Nathan Deal urging changes.

“The restrictions on ‘paid issue advocacy’ outlined in SB 127 exist nowhere else in the nation,” the groups wrote. “In expanding the definition of “communications” nonprofits can employ to educate the public on their position on a wide range of issues, this bill seeks to restrict civic engagement from organizations across the political spectrum.”

Advocacy groups, most who had not been following the legislation until this week, rushed to organize last-minute resistance to the bill.

Tanya Ditty, state director of Concerned Women for America, said she got an email about the bill at 9 p.m. Wednesday warning her about the provision that could require groups like hers to disclose their expenses and their donors.

“I’m not familiar with anything else about the bill,” she said.

Grover Norquist, founder of Washington-based Americans for Tax Reform, sees the provision as an attempt to discourage him and his organization from criticizing lawmakers who voted for this year’s massive transportation bill.

“Not only do these politicians want to raise taxes, they want to prevent anyone from pointing out to their voters that they raised taxes,” he said. “How ashamed they must be.”

Ditty fears donors to political causes, such as her own mother, could be subjected to reprisals if their names were disclosed.

“She’s 81-years-old,” she said. “A lot of people donate because they believe in the cause. We don’t sell our lists.”

Ditty said a disclosure of donors to groups supporting California’s Proposition 8, which outlawed same-sex marriage in that state, were subjected to abuse from opponents of the measure.

“This bullies us and backs us into a corner to keep us quiet,” she said of the Georgia proposal.

Another item tucked into the House version of the bill changes campaign finance rules to allow a party caucus — a faction of legislators drawn from the House or the Senate and affiliated with a particular party — to make unlimited donations to a party ticket or group of candidates.

The negotiations continue between House and Senate conferees, but time is running out. Lawmakers must adjourn for the year by midnight.