American organized-labor officials have issued a veiled warning to companies that manage union pension investments: back President Bush’s plan to create private Social Security accounts, and you may lose our business.

The American Federation of State, County and Municipal Employees and the Laborers International Union have written executives such as Morgan Stanley Chairman Philip Purcell and Charles Schwab’s chairman, Charles Schwab, to criticize Mr. Bush’s proposal to build private accounts into the 70-year-old retirement system.

“Our trustees feel it’s their fiduciary responsibility to make sure the investment managers they use are fully supportive of retirement security,” said the director of pension policy for the 1.4-million-member Afscme, Rich Ferlauto. “They want to get the information first before deciding whether to review contracts.”

American unions, which have $400 billion invested in pension plans, already have pressured one firm – St Louis-based Edward Jones & Company, the nation’s largest operator of retail brokerage offices – to withdraw from the leading industry group pushing for the private accounts.

The letter-writing campaign raises the stakes in a debate that pits Democrats, organized labor, and senior-citizen groups against Mr. Bush, Republican lawmakers, and business associations. Both sides plan to spend tens of millions of dollars lobbying on the Social Security issue, the president’s chief domestic priority.

Mr. Bush is already facing dwindling public support for his plan to redirect part of the 12.4% payroll tax into stocks and bonds. A February 24-28 poll by CBS News and the New York Times released March 2 found 31% of respondents confident in his Social Security decisions, while 63% said they were uneasy.

In a poll released March 3 by Westhill Partners and National Journal magazine, 61% said they disapprove of the way he’s handling the retirement program, up from 52% in January.

At least 100 financial services companies have been contacted by their union clients during the past two months, including Baltimore-based T. Rowe Price Group Inc. and New York based Merrill Lynch & Company and JPMorgan Chase & Company, according to the AFL-CIO, the nation’s largest labor organization.

Those firms should be concerned about their union customers, who say Mr. Bush’s plan would put at risk the Social Security income their members rely on, said Greg Valliere, chief political strategist at Stanford Washington Research, an investment-consulting firm in Washington.

“There is an enormous amount of labor-union money being run by financial services firms,” Mr. Valliere said. “Why antagonize a big chunk of your client base?”

The director of investment at the AFL-CIO, Bill Patterson, said the companies may have a conflict of interest in both managing union money and backing the president’s proposal, because Mr. Bush’s plan would directly benefit them.

“You expect them to be able to put the interests of the investing public or their clients ahead of whatever parochial interests they have,” Mr. Patterson said.

The Securities Industry Association estimates that Mr. Bush’s plan would generate $39 billion over 75 years for fund-management companies. Roger Hickey, director of the New Century Alliance for Social Security, a coalition of opponents, said the group is “low-balling this thing dramatically,” so it won’t look as if companies will profit much.

The union letters are “a form of economic intimidation,” said Bill Shipman, a former principal at Boston based State Street Global Advisors, a unit of State Street Corporation.

“What labor appears to be saying is that if you consider reforming the system along the lines of market-based investing, not only do we disagree with that, but we will punish you,” said Mr. Shipman, whose former employer previously came under attack by the AFL-CIO.

In 1996, Mr. Shipman and Marshall Carter, then State Street’s chairman and chief executive, co-wrote a book that advocated private accounts. In 2002, after the AFL-CIO protested State Street’s support for the accounts and Carter and Shipman had retired, State Street said it no longer supported diverting payroll taxes to create private accounts, according to the AFL-CIO. Today, State Street says it doesn’t have a position on the issue, according to a spokeswoman, Arlene Roberts.

“The approach they’re taking on this is not to the benefit of the labor movement,” said Mr. Shipman, who started his own consulting company in Manchester, Mass., after leaving State Street about three years ago. “Those who try to stifle debate ultimately will lose.”

Trustees can weigh many details in determining which investment companies to hire, including a company’s position on Social Security, said Patrick McGurn, executive vice president of Institutional Shareholder Services, the largest proxy adviser to fund managers.

“Pension-fund trustees have very broad discretion in choosing managers,” Mr. McGurn said. “Performance tends to be similar for these funds. That stretches the number of issues that can come into the selection process.”

Edward Jones & Company learned that the hard way last month. The company began broadcasting internally a 33-minute video on February 8 laying out the need for steps to shore up Social Security and possible solutions, including private investment accounts.

Two days later, Edward Jones issued a statement saying it wasn’t renewing its membership in the Alliance for Worker Retirement Security, the main industry group lobbying for private accounts. The AFL-CIO had mounted a letter-writing campaign and picketed the video studio at the company, which had belonged to the alliance since 1998.

Edward Jones denies it had lent support to the Bush proposal. “We have not taken a position relative to any of the reform proposals because at this point they’re only concepts,” said a spokesman, John Boul.

An Ohio-based trustee of the Laborers International pension plan sent a letter dated February 24 to San Francisco-based Charles Schwab. “I am concerned about Schwab’s ties to efforts that are potentially injurious to the retirement security of our plan’s beneficiaries,” wrote John Kilbane. “I ask that Schwab eliminate actual or perceived conflicts between your firm’s activities and our interests as a client.”

The Laborers’ Union represents 800,000 workers, most of them in the highway and building construction trade.

A Schwab spokesman, Glen Mathison, said the union campaign was “misdirected” at his company.

“We haven’t taken a position on private accounts yet, and we may not take a position,” Mr. Mathison said.

Three trustees of the New York City Employees’ Retirement System sent a letter dated January 26 to Morgan Stanley’s Purcell. They asked the firm to sever any ties to groups promoting private accounts, which would be “injurious to Social Security,” according to the letter. A Morgan Stanley spokeswoman, Andrea Slattery, declined to comment.

Union officials say the letters are not a threat. “I wouldn’t characterize what we’re doing as a warning,” said Mr. Patterson of the AFL-CIO. “These are strong expressions of concern about retirement security.”

The assistant director of research and negotiations at Afscme in New York, Michael Musuraca, said support for private accounts is only one issue the unions are considering about the fund managers.

“You judge managers on a variety of factors,” including their support for the president’s plan, Mr. Musuraca said. “It’s one of the variables, but to say it is the pre-eminent variable, no.”

Most companies stand to lose more than they would gain by advocating for private accounts, said Jack Marco, chairman of Marco Consulting Group in Chicago, the largest consultant to pension plans that serve union workers and retirees.

“It makes absolutely no sense for any of them to stick their neck out and take a position waiting to get knocked off,” Mr. Marco said. “Why should they lose this business on the distant chance that they might get some business out of the privatized accounts?”

Mr. Shipman, the former State Street official, said many companies “have gotten into this without doing the research” on “what the pushback will be.”