SAN JUAN, Puerto Rico -- Andy Stern, the president of the Service Employees International Union, is moving to further consolidate bargaining and organizing efforts across industry lines, a move that could limit the power of local unions but give the union greater leverage with big employers.
The direction taken by the SEIU -- one of the nation's biggest and most innovative unions -- could influence other unions and the direction of the U.S. labor movement by shifting some control further away from union locals. The SEIU has 1.7 million members, according to the Labor Department.
Mr. Stern's proposals were overwhelmingly adopted at the union's convention after being challenged by a small but vocal group of members and officers. The group said the union's top-down approach excludes input from rank-and-file members. The opponents didn't have enough support to bring their own proposed overhauls to the floor of the convention, which is held every four years.
Mr. Stern and his slate of candidates running to fill the SEIU's 73-member executive board were also set to win re-election. All but one seat will be uncontested.
Mr. Stern has set a goal of adding 500,000 members to the SEIU in the next four years, with a focus on workers in health care and property services, such as janitors and security guards, and on public-sector employees.
In a major shift, each of the SEIU's locals will send a set percentage of their budgets, previously used to fund local organizing drives, to the international headquarters to fund industry-specific organizing campaigns.
Strategy for national organizing and bargaining decisions would be set largely by executive board members on three committees, chaired by appointees of Mr. Stern. He said the proposal guarantees participation by local union leaders and members in bargaining and organizing decisions.
Employer consultants expect more-aggressive campaigns against big service-sector employers as a result. "Corporate campaigns are going to increase" because SEIU leadership has greater authority to make the deals with employers, said Michael Lotito, a labor-law attorney with Jackson Lewis LLP. He called the SEIU "the most aggressive organizing union in the country" and added, "you have to admire their tactical brilliance."
Mr. Stern is presiding over the first SEIU convention since leading his union and others out of the AFL-CIO in a historic break three years ago. Since he became president of the SEIU in 1996, the union has added nearly 100,000 members a year. His approach has been to combine dozens of previously autonomous locals through a program adopted at the union's convention four years ago. Some changes have alienated some leaders who have lost their positions, as well as members who felt forced to merge.
On Monday, Mr. Stern justified his call for coordinating organizing nationally, as opposed to locally, saying it would result in more SEIU members and more members in organized labor in general, which in turn would raise standards for all workers.
"We must build a union that wins justice for us, but secures it by winning justice for all!" he said in a speech that drew the more than 3,000 SEIU members to their feet cheering several times.
Mr. Stern acknowledged the debate within the SEIU as part of a broader one within the labor movement, which now represents less than 8% of private-sector workers, a 50% drop from 25 years ago. He described union leaders who haven't focused on organizing new members as elitist and exclusionary. "History has shown no mercy for union leaders who tell members, 'We can survive forever as islands of strength in a nonunion sea.'"
Opponents say his approach minimizes input from local leaders and their members. They also contend SEIU leadership, under Mr. Stern, has been more willing to broker deals with employers and agree to trade-offs -- such as allowing subcontracting -- without consulting with members.
"The International wants to control all the deal-making authority with these employers to make secret deals to get access to organize more workers," said Sal Rosselli, Mr. Stern's chief critic. Mr. Rosselli heads a California local representing 150,000 health-care workers that spent $15,000 on billboards near the convention site and $10,000 on online ads and distributed 15,000 leaflets to convention-goers. He said he agreed with the goals outlined in Mr. Stern's speech, but said that "it can't be done top-down."
Another Stern proposal will replace the old system of shop stewards with "member resource centers," which members can contact through a 1-800 number, freeing up staff and funds for organizing. Mr. Stern compared the current model of representation at most unions to "a 1930s Teletype in a 21st-century Internet world."
Bruce Raynor, president of Unite Here, backed Mr. Stern's leadership in a speech at the convention. Mr. Raynor said deals reached by Unite Here and the SEIU with three big food and maintenance companies resulted in 15,000 new union members who won wage increases and health-care benefits. "It made a difference in their lives," he said.
Write to Kris Maher at kris.maher at wsj.com