Leaders of three business groups called yesterday for President Reagan and Congress to cut $50 billion from the projected $200 billion deficit for fiscal 1984 by lowering both domestic and military spending rather than by raising taxes.

The heads of the National Association of Manufacturers, the National Federation of Independent Business and the American Business Conference issued their call less than two weeks before the president is due to unveil his budget and two days before a large group of business executives, financiers, academics, lawyers and former government officials plans to run a national advertisement calling for spending cuts and tax increases to shrink the 1985 deficit to $75 billion.

At yesterday's press conference, the business groups called for defense cuts of between $18 billion and $23 billion, significantly more than the $8 billion Reagan has said he will request. They suggested that, in addition to a military pay freeze and cost savings from lower inflation, between $5 billion and $10 billion of cuts "can be found in the areas of operations, maintenance and other nonprocurement activities and up to $5 billion can be saved by cancellation or, more likely, deferral of weapons systems procurement."

The leaders--Alexander B. Trowbridge of the NAM, Arthur Levitt of the ABC and Mike McKevitt of the the NFIB--also proposed fiscal 1984 reductions of between $12 billion and $15 billion in nondefense discretionary programs and between $10 billion and $15 billion in entitlement programs.

They recommended, in particular, reductions in the cost-of-living adjustments to Social Security and other entitlement programs. (Reagan is considering a six-month postponement of these COLAs.)

The Chamber of Commerce, another leading business group, was not involved in yesterday's meeting.

The three groups holding the news conference strongly opposed new tax increases, with McKevitt also opposing the plan to advance by one year the Social Security payroll tax increases now scheduled for 1985, and to increase significantly the Social Security tax paid by the self-employed. He said that high payroll taxes lower employment by raising the cost of hiring workers.

Trowbridge said that the nation should unite behind a program to reduce the deficit.

This would enable the Federal Reserve Board to continue to bring interest rates down as the economy recovers, the three said.

"The best way to expand production and increase jobs is to bring interest rates down further, restore corporate liquidity and increase investment," Trowbridge said.

"The national security of this country will rest on a strong national economy," he said, defending the proposals to scale back military spending increases more than Reagan wants.

Trowbridge suggested that real growth in military spending, adjusted for inflation, could be kept to 5 percent a year rather than the 9 percent that was implicit in Reagan's earlier plans.