Opponents of the proposed merger between the Screen Actors Guild and the American Federation of Television & Radio Artists are asking for a federal court order to block the merger balloting.

The action was filed Wednesday in Los Angeles, with more than five dozen SAG members — including Martin Sheen, Ed Harris, Nancy Sinatra and former SAG presidents Ed Asner, Kathleen Nolan and Alan Rosenberg — as plaintiffs.

The action asserts that SAG is attempting to merge with AFTRA “without conducting the necessary due diligence.” The four-count civil complaint was filed against the guild, SAG national exec director David White and SAG president Ken Howard, SAG secretary treasurer Amy Aquino and SAG VPs Ned Vaughn, Mike Hodge and David Hartley-Margolin.

The complaint alleges three violations of federal labor law and one of California common law. It seeks an injunction to prevent a vote until SAG completes the “required due diligence,” including completion of an independent study detailing the actuarial effect of the merger on the SAG and AFTRA pension and health plans; “full and fair” disclosure of all aspects of the merger plan; “full and fair disclosure” of access to membership lists; and a “legally valid” election procedure.

In a statement, SAG vowed to “vigorously” fight the action, calling it “a clear attempt at circumventing the will of the membership.” The guild said it was confident that all of its actions in regard to the merger process were in keeping with its rules, and it emphasized that it has held more than 50 informational meetings around the country in the run-up to the merger referendum.

“This filing is simply a public relations stunt that follows a clear pattern by some of the plaintiffs of filing unsuccessful lawsuits against their own union,” the statement said.

AFTRA had no comment.

SAG and AFTRA are scheduled to mail out ballots Monday to 120,000 SAG members and 70,000 AFTRA members, who include actors, broadcasters, DJs, singers and dancers, with a tabulation date of March 30. To be approved, the merger must receive at least 60% of the votes from each union.

SAG members voted down proposed mergers in 1999 and 2003.

Plaintiffs’ attorney David Casselman of Wasserman, Comden, Casselman & Esensten told Variety he’s expecting a hearing to be set within the next two to three weeks. He noted that the suit’s attempting to delay the vote until SAG revises its procedures, rather than prevent SAG from mailing out the ballots.

“We have spent almost two months negotiating with SAG in an effort to get them to present the truth regarding this merger plan. Members are entitled to full disclosure, not half-truths and misleading and unsupported promises,” Casselman said. “They have done nothing of substance to support their claims that the proposed merger will protect SAG member benefits. The average SAG member makes less than $10,000 per year. They need to know that all necessary due diligence was done to protect them.”

Merger backers have gained endorsements from hundreds of members — including George Clooney, Robert De Niro, Tom Hanks, Octavia Spencer and Betty White.

“A merger of AFTRA and SAG will increase our bargaining strength and give us more power to safeguard our wages, residuals, working conditions and, of course, our benefits of health and retirement (pension and health),” the endorsement statement says. “Our employers operate across all types of media. We must have the power to meet them as one union with one voice.”

Opponents have been tussling with SAG in recent weeks over the wording in the 18 pages of ballot materials that are set to go to members on Feb. 27 — particularly the lack of a comprehensive analysis of combining the SAG and AFTRA pension and health plans and the assertions by the unions in their feasibility study.

The unions’ summary of the feasibility study — which contains opinions of seven attorneys with experience in the field — noted that several hundred multiemployer pensions have merged over the past 25 years, and there is no legal obstacle to merging the SAG and AFTRA pension and health plans. It also said multiemployer plan mergers do not pose any increased risk of loss of benefits.

Merger opponents have contended that the combo of unions will not solve problems in such areas as split SAG and AFTRA earnings on pension and health contributions and will not lead to increased negotiating strength. But candidates backing merger have won nearly all the seats in recent elections.

The federal court complaint asserts that the SAG constitution recognizes that careful study of any SAG-AFTRA merger plan would be necessary “to satisfy the requirements of law and the protection of all eligible members against the loss of benefits, presently or in the future.”

The SAG national board voted on Jan. 28 to approve the proposed merger plan. Howard touted the plan the next day on the televised SAG Awards, saying that the “historic step” of merger was about to be realized.

“We believe the defendants made this announcement in order to thoroughly saturate the media with pro-merger propaganda, avoiding any balancing information which would allow SAG members to intelligently evaluate the issues prior to voting,” Casselman said. “If an uninformed membership approves this merger, and then we all learn that it will have crippling, negative effects, it will be too late for anything to be done to return SAG or its current pension and health plans back to their current status.”

The suit said the merger is being presented in a deceptive manner and noted that the current elected officials of SAG will remain in their posts until 2013 if the merger’s approved.

“Defendants have ignored their obligations as fiduciaries, promoting a merger while obfuscating the truth,” the action said. “Along with the proposed merger of the unions, an entire slate of new joint union board members and officers will be seated. No opposing candidates are even permitted to run or campaign.”

Other plaintiffs include Valerie Harper, Clancy Brown, James Remar, George Coe, Diane Ladd, Lainie Kazan, Nichelle Nichols, Renee Aubry, Jane Austin, Erick Avari, Steve Barr, Sara Barrett, Terrance Beason, Michael Bell, Warren Berlinger, Joe Bologna, Ralph Brennen, Alexandra Castro, Jude Ciccolella, Cynthia Lea Clark, David Clennon, Joe D’Angerio, Patricia D’Arbanville, Dick Gautier, Dorothy Goulah, Marty Grey, Sumi Haru, Angel Harper, Basil Hoffman, David Huddleston, Anne-Marie Johnson, David Jolliffe, Kerrie Keane, Peter Kwong, Kurt Lott, Barbara Luna, Eric Lutes, Stephen Mach, Michael McConnohie, Peter Antico, Susan McNabb, Phyllis Timbes, Marguerite Moreau, Traci Murray, Nicole Mandich, Larry Newman, Barbara Niven, Jack Ong, Peggy Lane O’Rourke, Leslie Parrish, Scott Pierce, Robin Riker, Stephanie Rose, Alan Ruck, Wendy Schaal, Tascha Schaal, Cynthia Steele, Renee Taylor, Malachi Throne, Beverly Todd, Jessica Wright, Momo Yashimo, Barry Brandt and Paul Edney.

Sally Field and board member Adam Arkin blasted the suit and the plaintiffs.

“I’d like to say I’m shocked, but I’m not,” she said. “It’s the same tired junk from the same group. It’s a waste of the members’ resources and will ultimately amount to nothing. It’s just cynical, and sad, and all too predictable. I hope they will please just stop and help us have one strong union.”

Arkin’s statement referred to an unsuccessful 2009 lawsuit against SAG by Rosenberg to overturn the national board’s firing of Doug Allen from the post of national exec director.

“They have no qualms about wasting the members’ resources with a frivolous – even ridiculous – lawsuit,” he said. “We’ve seen it from these people before, but frankly it’s just astonishing that they continue to use the courtroom as a weapon against SAG members. It’s completely counter to the will of the the overwhelming majority of members, who have repeatedly elected pro-merger candidates. It’s clear they don’t want members deciding the issue.”