Corporations, trade associations, unions, federal agencies and, in one case, a foreign government--all normally barred from making contributions to individual congressmen--provided about $1.8 million last year to support the work of congressional caucuses, House records indicate.

Congress provided many of these same caucuses with free office space and an estimated $1.5 million in staff salaries. However, it has done little to regulate the caucuses, some of which often operate as in-house special interest lobbying groups.

This has allowed such caucuses, which have mushroomed to about 60 during recent years, to operate in a legal gray area, and has provided special interests another way to influence legislation.

Under congressional rules, individual members of Congress are prohibited from accepting donations from corporations, unions, federal agencies or foreign governments. But, because there is no specific regulation banning such donations to groups of congressmen, caucuses routinely accept such contributions.

House records, for example, show the Congressional Black Caucus last year accepted a $1,500 contribution from the government of Haiti, and its chairman, D.C. Del. Walter E. Fauntroy, says the caucus has received donations from "just about every black nation in Africa" in the past. The U.S. Constitution prohibits any officeholder from accepting "any present, emolument, office or title" from any foreign state, but like the congressional rules, it is silent on the issue of caucuses.

Contributions from groups having a direct interest in legislation are widespread. The Travel and Tourism Caucus, for example, works as the eyes and ears of the tourist industry on Capitol Hill. House records show it received more than $480,000 during the last 18 months from the giants of that industry: Holiday Inns, Howard Johnson, Pan American Airways, Eastern Airlines, Greyhound, Trailways Bus, Hilton, Sheraton, Resorts International and Ceasar's Palace Hotel among them.

Some caucuses have developed a cozy relationship with federal agencies, which raises serious questions about the separation of the legislative and executive departments of government. This year these groups will receive an estimated $1 million in federal grants.

The Environmental Study Conference, for example, reported contributions of $1,000 each last year from the Department of Agriculture and the U.S. Geological Survey, although federal agencies are prohibited by law from engaging in lobbying activities.

The Northeast-Midwest Coalition and several other caucuses have set up separate tax exempt "research institutes" to avoid the appearance of conflict of interest. But even here there are problems. Although spokesmen claim the institutes operate separately from the coalition, they work in adjoining offices furnished by Congress and have the same phone number.

This year the Northeast-Midwest Institute received a $100,000 grant from the Economic Development Administration (EDA) and a $180,000 grant from the Department of Housing and Urban Development. When the Reagan administration tried to kill EDA earlier this year, Rep. Robert W. Edgar (D-Pa.), chairman of the Northeast-Midwest Coalition, castigated budget cutter David Stockman for the move during a House hearing.

He repeatedly cited results of a study praising EDA. Who did the study? The Northeast-Midwest Institute. It was paid for with foundation funds.

Caucuses are a recent phenomenon on Capitol Hill. In 1969, there were only three.

There are caucuses for women and Hispanics, shipyards and steel, textiles and coal. There are caucuses for solar energy, mushrooms, the arts, jewelry manufacturers, the Irish, the Sun Belt, New Englanders, westerners, civil servants, senior citizens, suburbia, rural America, liberal Republicans and conservative Republicans, and Democrats of every stripe.

Many of these groups operate entirely with congressional funds, and have become an indispensable part of the legislative process. The Democratic Study Group, for example, was the first caucus, formed by liberal Democratic congressmen in 1959. Its research and daily analysis of pending legislation is considered so valuable that every Democrat, and 20 Republicans, subscribes to its service.

Until recently, the House has shown little interest in setting standards for the dozens of caucuses that have sprung up in recent years. The only comprehensive effort failed in 1977. But several months ago the Better Government Association, a privately financed group with an impressive track record for hardhitting investigations, began a probe of the caucuses.

Responding to this, the House Administration Committee has scheduled a hearing on the matter Tuesday, and has circulated a draft of proposed regulations. The most controversial of the regulations would bar caucuses receiving outside money from operating in offices supplied by Congress and using staff members paid for by Congress.

Fauntroy, in an interview, said this would discriminate against the black, women's and Hispanic caucuses, which have few members inside Congress but represent large numbers of Americans. There are 20 blacks in the Congress, 20 women and six Hispanics.

As might be expected, the black and Hispanic caucuses receive substantial amounts of money from labor unions, civil rights groups, black and Hispanic organizations and prominent black and Hispanic Americans.

But both are largely financed by corporate America, according to House records. One fourth of the $26,000 in contributions the Hispanic caucus reported in 1980 came from giant corporations.

More than a third of the $580,000 raised by the black caucus, primarily at its annual dinner, came from corporate America.

Media organizations also contributed heavily. Among those giving $1,500 or more were: The Washington Post, CBS, ABC, NBC, WDVM-TV, WJLA-TV and Johnson Publications, which publishes Ebony and other black-related magazines.