Former criminals shielded by the federal Witness Protection Program have been allowed to evade millions of dollars in debts and to ignore court decrees ordering them to turn over children to divorced or separated spouses, according to a General Accounting Office study.

The study, obtained by The Washington Post, also found that "it was not uncommon" for the witnesses to commit new crimes. The GAO said seven witnesses have been convicted of murder, another has been charged with murder and four others may have been "involved with murders."

Under the program run by the U.S. Marshals Service protected witnesses are relocated by the government with a new identity after testimony against former criminal associates. More than 90 percent come from criminal pasts. Most are poorly educated with few job skills.

When the program began 12 years ago it was expected to handle 25 to 50 witnesses a year. Instead, more than 300 enter each year, with a total of 4,300 since 1970. The annual budget has reached $28 million.

The Justice Department, in response to the GAO report, said the program is difficult to run. But it said many problems, particularly debt collection and child custody rights, were resolved a year ago with an internal memorandum giving program officials authority to disclose the names of witnesses who refuse to obey court orders.

The GAO would like to see the policy spelled out in legislation, and its report recommends setting up a judicial review mechanism for cases in which Justice refuses to identify an uncooperative witness.

Sen. Max Baucus (D-Mont.), who initially requested the GAO study in 1979, will introduce legislation early next week following the GAO recommendations.

"The program is trampling on the rights of parents of relocated children and unsuspecting creditors," Baucus said yesterday. "Congress needs to make changes to . . . give innocent third parties the right to impartial counsel in order to recover their losses. The . . . program is an important tool in our anti-crime effort. But it should not violate the rights of law-abiding, innocent persons."

Kevin Rooney, assistant attorney general for administration, said such legislation could produce "unnecessary and possibly lengthy litigation, further burdening the judicial system." He said Justice needs more time to "demonstrate that its new policy will alleviate these concerns."

Howard Safir, an assistant director of the Marshals Service and the head of the witness program, said many problems have been corrected since the GAO began its study. But he conceded that the program has been a difficult operation because of the participants' backgrounds and the trauma involved in uprooting families, cutting their ties with relatives and friends and trying to set them up in new communities with new names.

The GAO study documented 10 cases in which relocated parents disappeared with children, in violation of court orders dealing with custody or visitation rights of the other parent. In seven of those cases the parent was reunited with the child after periods of two months to nine years. In the other three, the children had still not been returned, despite court orders.

One case involves Donna Ruffalo of Kansas City, whose ex-husband disappeared with her son into the witness program in 1978 although she had legal custody. She still has not seen the child, who is now 13. The marshals service has refused to tell her where the child is.

George Kannar, the American Civil Liberties Union lawyer representing Ruffalo in a lawsuit against the Justice Department, has argued that parents have a right to a hearing before a child can be taken away by the federal government. Last month a federal appeals court found that Ruffalo's constitutional right to due process was violated when her son was taken without any hearing. The case was sent back to U.S. District Court, where it is scheduled for trial next month.

Safir said he could not talk about the Ruffalo case, but added that marshals simply deliver court orders to witnesses and "have absolutely no legal authority to make any witness do anything."

He said custody records are carefully checked before witnesses enter the program. "We don't want to be in the business of taking children away from people who have legal custody," he said.

The GAO also found that in a six-month period in 1980 creditors tried to collect $7.3 million in debts from 32 relocated witnesses.

"The policy is that if it's egregious, and the witness has the capacity to pay and refuses, we tell him we will reveal his location to the creditor," Safir said, adding that most witnesses comply.

Asked about witnesses who commit new crimes, Safir agreed that a problem exists, but said he believes it is outweighed by the program's benefits. "It's very effective as far as putting major criminals in jail," he said.

A marshals service study last year found that 17 percent of the relocated witnesses had been arrested since they were admitted to the program. To combat that problem, the Justice Department has started psychological screening and counseling to try to predict which witnesses may commit crimes and need special supervision.

Safir added that local police are provided with the criminal records of witnesses who commit felonies. But the GAO complained, "The department did not effectively track criminal arrests of protected witnesses . . . . Although the marshals service had attempted to establish an arrest log, the log was not very useful because it was not consistently prepared or maintained."