The Soviet Union, the leading non-African supporter of guerrilla forces seeking to overthrow the white-minority government of Rhodesia, has been accused along with four other East European countries of conducting "regular trade" with Rhodesia in a "major sanctions-breaking operation."

The charge emerged in a limited distribution annual report issued last month by the U.N. Security Council's committee to police economic sanctions against Rhodesia imposed by the United Nations in 1966. The report was not distributed to the press.

The accusation, submitted to the U.N. Sanctions Committee by the British government in September, was one of four British diplomatic notes over the past year that have alleged specific trade relationships between Rhodesia and companies controlled by Soviet bloc governments. Together, they indicate a broad pattern of sanctions-breaking by the Soviet bloc.

Failure of the U.N. sanctions against Rhodesia over the last decade has been generally acknowledged but previously most sanction-breaking had been laid to Western nations. The Soviet Union has criticized the United States frequently for openly importing Rhodesian chrome, despite the U.N. ban, as a result of Congress' passage in 1971 of the Byrd Amendment.

The United Nations has often criticized the West for trading with Rhodesia but the documented British accusations represent the first hard evidence of Soviet and East European trade with Rhodesia.

The Soviet Union and Romania, both members of the Sanctions Committee, have denied the allegations while the other East European nations named - East Germany, Czechoslovakia and Bulgaria - have not replied.

Although the formal British notes do not explicity accuse these nations of knowingly tradi* ng with Rhodesia, one diplomat on the Sanctions Committee said, "If they didn't know it was because they hadn't asked the questions that they didn't want answered."

The major British allegation involving the Soviet Union was linked to a Rhodesian trading agency, Michelle Enterprises, Ltd., which allegedly exported "tobacco and other agricultural commodities from Rhodesia and, in turn, imported chemicals, metals and agricultural requirements from Eastern Europe," according to the U.N. report.

The amounts involved and the nature of the Soviet chemicals and metals allegedly traded to Rhodesia were not specified, except for a general description of the trade as "major."

Rhodesia's high-quality tobacco has continued to reach world markets and has been a major factor in maintaining the Rhodesian economy, despite sanctions. The network used to export the tobacco has never been exposed, however.

It is apparent from the quiet way that the Sanctions Committee circulated the British allegations that it did not want to embarass the Soviet Union. The trade between Rhodesia and the Soviet bloc came to general public attention as a result of investigative reporting by Eric Malling of the Candian Broadcasting Corporation's public affairs program, "the fifth estate" televised yesterday in Canada.

The trade was allegedly conducted through three Geneva-based companies, set up specifically for the purpose - Comaisa, Tobatrade and Centrex. It involved, the U.N. committee was told, the sale in Eastern Europe of cigarettes made from Rhodesian tobacco and packaged with striking realism under the names Benson & Hedges, Pall Mall, Lucky Strike, Chesterfield and State Express - all fraudulently purporting to have been manufactured in the United States and Britain.

A subsequent British note to the U.N. committee sent on Dec. 15, alleged that the Soviet state-owned trading company, All-Union Corporation For Trade in Miscellaneous Goods, and the Bulgarian state tobacco trading company, had entered negotiations through a Geneva company, Intabex, to buy Rhodesian tobacco from the Rhodesian company Tradim-pex.

Two other British notes to the U.N. committee implicated other Eastern European nations in trade with Rhodesia.

One, submitted in April, noted that the C.Z. Scientific Instruments, identified as a British-based subsidary of the East German company Carl Zeiss of Jena, had been fined $10,000 after pleading guilty in a British court to sanctions-breaking.

The East Germans denied involvement in the Rhodesia trade conducted by the corporation. Britian replied with documentation on the extensive East German shareholdings in and managerial control of the British company.

The most recent British note, submitted just last month, alleges that a Liechtenstein-based firm called Tobmark, Ltd., "collects orders and negotiates contracts" for the Rhodesian tobacco trading company called Trading Enterprises, Ltd. Among the Rhodesian customers, the note says, are the Tobacco State Enterprise of Iraq, and Tabak DSO Bulgarskitutini of Sofia, Bulgaria.

The U.N. Sanctions Committee, which meets in secret and is composed of all 15 members of the Security Council, has no power to halt sanctions violations. The report also disclosed that the committee had considered 58 new cases of sanctions-breaking last year. Other countries charged included West Germany, Belgium, Italy, Japan, Switzerland, several African nations, Turkey, Iraq, Israel and the United States.