Two congressman and a trade union leader arrested Friday for demonstrating outside the South African embassy were released yesterday without court arraignment after the U.S. attorney's office declined to file formal complaints against them.

One of those released, Rep. George W. Crockett Jr. (D-Mich.), described the action by prosecutors as "part of an effort by the Reagan administration through the State Department and the Justice Department to belittle the importance of what we are are doing."

Crockett, Rep. Don Edward (D-Calif.), the first white congressman to demonstrate, and Leonard Ball, national coordinator of the Coalition of Black Trade Unionists, were arrested Friday for refusing to leave the front of the embassy. The three spent Friday night in a 2nd District police cellblock.

Crockett, a former judge from Detroit, accused the administration of "trying to get out from under the pressure of all the people who were on the picket line" in front of the embassy compound on Massachusetts Avenue NW last week.

The U.S. attorney's office on Friday dropped charges against 11 other persons arrested previously at the embassy during demonstrations to protest South Africa's apartheid policy of racial segregation.

U.S. Attorney Joseph E. diGenova, responding to Crockett's remarks, said, "All the decisions in these cases have been made by the U.S. attorney alone without any consultation from anybody in the White House, the State Department or the Justice Department."

Sources close to the office said prosecutors say the embassy charges would result only in "show trials" that would focus attention on the apartheid policies of the South African government and gain little in terms of law enforcement.

Given an existing backlog of serious drug and other major crime cases, sources said, diGenova is not anxious to clog the city's courtrooms with defendants arrested in a symbolic, nonviolent protest against racial oppression. "If the congressman would like to come down and take a look at our docket, he's welcome," diGenova said.

Crockett said, "I think he [diGenova] is lying, and I have my experience in the criminal justice process."

Crockett, Edwards and Ball appeared yesterday before a D.C. Superior Court judge who apologized for holding them in a cell several hours before calling their cases.

Prosecutors yesterday morning told the court they would not file complaints in the cases, permitting the release of all three defendants.

Police had charged them with congregating within 500 feet of a foreign embassy, an offense punishable by 60 days in jail and a $100 fine. Crockett told Judge George W. Mitchell that his arrest and detention "was in violation of the law and in violation of my constitutional rights."

Meanwhile, Rep. John Conyers (D-Mich.) and William Simons, president of the Washington Teachers Union, face prosecution by the D.C. Corporation Counsel on charges of violating a police barrier, for which they face possible fines of $300.

Outside court, Crockett was embraced by D.C. Del. Walter E. Fauntroy, a leader of the protests who last week was arrested on a charge of unlawful entry at the embassy. Fauntroy's charge has also been dropped by prosecutors.

Fauntroy, who was joined at the courthouse by Randall Robinson, executive director of the TransAfrica lobbying group and another of those arrested, declined to comment on the actions of the U.S. attorney's office pending a news conference scheduled for tomorrow.