Washington — The US Office of Management and Budget (OMB) is swimming in letters, messages , and protests this week. And the deluge has nothing to do with budget cuts or controversial director David Stockman.
At stake is at least $80 million that federal workers donate to charity through payroll deductions. A Reagan administration proposal would cut out of the campaign a number of groups, especially those lobbying for legal rights.
''We've gotten more comments on that [proposal] than on the tax bill and budget reconciliation combined,'' says Michael Horowitz, special counsel at the OMB. National charities and virtually all of their local chapters have poured in comments on the proposed changes.
During the next week Mr. Horowitz says he will draft a memo to President Reagan listing options for resolving the dispute.
The flak began when Donald J. Devine, director of the Office of Personnel Management (OPM), drafted a proposed new executive order on the federal charity program. Mr. Devine called for focusing only on ''health and welfare'' agencies. He called for excluding civil rights groups and other ''advocacy'' groups from the list of charities that federal workers can give to by payroll deduction.
Among the groups cut out would be the NAACP Legal Defense and Educational Fund, the National Organization for Women (NOW) Legal Defense and Education Fund , and the National Resources Defense Council.
Devine also proposed excluding any agency that gives abortion services or abortion counseling. The OMB, which is processing the new executive order, erased the antiabortion language without commenting, but the issue is still unresolved.
Critics charge that Devine, who has been active in the antiabortion movement, designed the new guidelines mainly to kick out groups such as Planned Parenthood.
''Sure he wanted abortion out,'' says OPM spokesman Patrick S. Korten, who adds that his agency is not happy that OMB struck the provisions against abortion groups. He says that OPM will take its case directly to the President. However, Mr. Korten maintains that abortion was not Devine's chief concern.
''The major factor is the legal defense and education groups, the groups involved in litigation and lobbying,'' he says.
Some of these ''advocacy'' groups have recently sued successfully to be included in the federal payroll campaign, which raised $83 million for charities in 1979, the latest year for which there is an official total. ''The floodgates were really going to open this year,'' says Korten, charging these new groups would ''dilute'' the charity campaign.
''This would cause a lot of employees not to participate,'' he says. ''They would say, 'Heck, half of my money is going to the NOW Legal Defense Fund.' '' The fact that employees can pick the charity they are giving to would not resolve the problem, says Korten.
Rep. Patricia Schroeder (D) of Colorado, who chairs the House civil service subcommittee, assails the OPM proposal. ''It's paternalistic for the federal government to start dictating who you give to and who you don't.''
Women should have a choice of giving to women's groups and blacks to black organizations, including legal defense funds, she says.
A big winner in the proposed new charity campaign program would probably be the United Way, the biggest combined charity fund in the US. In most areas the local United Way fund would be given the job of distributing the undesignated donations from the federal employees. United Way of America backs plans to limit the federal campaign to health and welfare agencies. ''I think the government has to exercise some responsibility with respect to work-place charitable programs,'' says Jerry Bergman, spokesman for the organization. The employer has to run the program ''in a way to best serve the public interest,'' he says.
The National Committee for Responsive Philanthropy charges that groups like United Ways do not give enough money to minorities, women, and less-traditional charities.