The Office of Management and Budget yesterday moved to derail efforts planned by congressional Democrats this week to restore the $122-a-month Social Security minimum now received by 3 million beneficiaries. $1

A statement issued by OMB said the minimum, which is slated to be dropped under the House and Senate spending cut bills, is a "pure 'windfall' for recipients" that would cost $7 billion over the next five years. The additional cost would make "the Social Security financing crisis that much more acute and jeopardize benefits of those who earned them."

At issue is only whether the minimum should be preserved for those who now receive it. Even House Democrats have proposed eliminating it for future recipients.

Because the minimum is received by those who would earn less by the conventional formula, OMB termed it "an unearned benefit." Among those who receive the minimum, OMB said, 300,000 would feel the effect of the cutback. Even those could not fall below a "safety net" of supplementary security income, food stamps and medicaid that stands at about $10,600 per couple per year, OMB said.

Of the other 2.7 million recipients of the Social Security minimum, OMB said:

1.7 million would be unaffected because they receive more than the minimum through an accounting technicality, because they earn an amount nearly equal to the minimum by the standard formula, or because they receive supplementary security income benefits that will make up the money lost from Social Security.

800,000 receive pensions or have spouses who work or receive pensions. The OMB said the average of these people's total incomes is above $20,000.

200,000 are college students or children below the age of 18 whose families have outside incomes.

House Majority Leader James C. Wright (D-Tex.), who led the move Thursday to reinstate the Social Security minimum in pending legislation, responded, "The mathematical gyrations of the OMB never cease to amaze me. The fact remains that most of the people adversely affected are among the poorest and the oldest and the most politically defenseless in our society."

Wright said that if so many people would be unaffected, the resulting savings would not be large. "You can't have it both ways," he said. "If the government saves money at the expense of these elderly Americans, then the elderly Americans obviously most lose the money that is saved."