Congressional trips abroad, while frequently yielding legislators important information, remain a fertile field for abuse by some members who travel in unnecessarily large groups, make unnecessary use of expensive military aircraft or provide scant justification for their wanderings, according to a report released yesterday by Congress Watch.

The study revealed that the most popular destinations for House members in the 30 months ended June 30 were France, Italy and Greece, while senators traveled most often to France and Britain.

No Central American country ranked in the top 10 of the study's listings for congressional travel in 1982 and 1983, although Mexico was host to 34 House members in 1981, making it the seventh most popular destination that year.

While 44 percent of House members and 37 percent of senators reported no travel during the period studied, their colleagues reported 991 trips to 114 countries, according to summaries in the report.

In the Senate, the Foreign Relations and Armed Services committees sent more members traveling in 1981 and 1982 than other panels; the Appropriations Committee was third.

Foreign Relations and Armed Services have jurisdiction, respectively, over legislation authorizing foreign aid and military aid. The Appropriations Committee handles legislation appropriating foreign and military aid.

In the House, the Armed Services Committee sent more members abroad in 1981 and 1982 than any other panel, with the Appropriations and Foreign Affairs committees trading third and second places on the list during the 2 1/2-year period.

Congressional travel has been a popular subject for scrutiny for more than 20 years, since the late representative Adam Clayton Powell (D-N.Y.), flamboyant chairman of the House Education and Labor Committee, drew public attention with a junket to the nightclubs of Paris, a Venice film festival and the Greek islands.

But, according to the recent report by Congress Watch, a lobbying group founded by Ralph Nader, documentation of congressional trips and expenses is still scanty. The group recommends limits on the expenses of each member of a congressional delegation traveling abroad, restrictions on the use of military aircraft, new conditions for lame-duck travel and requiring the justification of a trip's purpose, objectives and probable cost.

Currently, a representative or senator wishing to travel abroad at congressional expense must obtain authorization from his committee or subcommittee chairman and, in some cases, from the panel's ranking minority member as well.

The Congress Watch report said that:

* Rep. E. (Kika) de la Garza (D-Tex.), chairman of the House Agriculture Committee and one of the most frequent travelers, made plans to lead a delegation to the Soviet Union in 1981 to "study various agricultural problems and activities" there, but after a visa problem developed went instead to Copenhagen, Budapest, Istanbul, Athens and Madrid.

* The two senators who traveled most in the 30 months, Charles McC. Mathias Jr. (R-Md.) and Claiborne Pell (D-R.I.), are members of the Foreign Relations Committee. Two of Pell's eight trips were to Latin America, the remainder to western Europe. One of Mathias' trips took him to the Soviet Union, the remaining eight were to western Europe.

* In August, 1981, Rep. William L. Dickinson (R-Ala.) led a nine-person delegation to Bermuda and Panama. The purpose of the trip was listed as "committee business" of the House Armed Services Committee. Use of a C9 military jet cost $20,913, the equivalent of more than $2,100 in airfare for each travelers; the military escort spent $2,130 for supplies, tips and in-flight expenses while delegation members collected $645 each in per diem costs.

* Rep. Clarence D. Long (D-Md.), who chairs the foreign operations subcommittee of the Appropriations Committee, took five trips of which two were to Europe. Long, who has had a role in the negotiations over foreign aid to Central America recently, went twice to Mexico last winter and once to Guatemala, Honduras, Nicaragua, Costa Rica and El Salvador.

* Rep. Michael D. Barnes (D-Md.), chairman of the Foreign Relations subcommittee on Western Hemisphere affairs, took seven trips, one to Canada and the remainder to Latin America, traveling to 16 countries, including two visits to Costa Rica, Nicaragua and the Dominican Republic.

* Sen. Alfonse M. D'Amato (R-N.Y.) took his father and administrative assistant on a trip to Rome, Naples and "other places as necessary" in Italy to present a check for disaster relief funds.

In addition, the study showed seven lame-duck members of Congess took a total of 10 trips abroad last year to destinations that included Italy, France, Britain and Switzerland.

"We're concerned because we think there are very important reasons for going to different places, but there clearly are abuses," said Congress Watch President Joan Claybrook, who headed the National Highway Traffic Safety Administration during the Carter administration. "Without rational disclosure policies, it's not possible to tell them apart.

"There's no place where everyone explains why trips are taken and what the purpose is; there are no reports written . . . . If you have enough disclosure and basic policies to handle some of the worst abuses, congressional travel won't be so tainted. Now I feel there is a taint," Claybrook said.

Congress Watch researchers found that the normal $75 per diem for legislators is frequently supplemented by hundreds of dollars worth of food, liquor and other expenses picked up by the State Department or military escorts.

Half of the congressional travel involved staff rather than legislators, according to the report.

Scott Cohen, staff director of the Senate Foreign Relations Committee, said his panel's travel "is almost always justified because we have oversight responsibility for foreign policy. The proof is in the quality of the reporting when people come back."