Government prosecutors yesterday accused Mary Treadwell, executive director of Youth Pride Inc., of a 15-month "concerted effort to delay and frustrate" their grand jury investigation, and asked a federal judge to find her in contempt of court if she does not cooperate immediately.

In a rare public filing of court papers in connection with the probe, the U.S. attorney's office said that Treadwell has failed to fully comply with four subpoenas asking her to appear before the grand jury and certify that she is the custodian of Pride-related business records, and provide a sample of her handwriting. The first subpoena was issued in November 1979.

The grand jury has eventually received the records it requested, though at times after lengthly delays. But Treadwell has never come before the panel to formally acknowledge that she is the official custodian of the records of numerous spinoff organizations of Youth Pride that are under scrutiny in the wide-ranging investigation. Such a declaration is usually routine.

The move by federal prosecutors to complete this phase of the grand jury's indication that the voluminous and well-publicized investigation is moving into its final stages, despite several delays.

The Washington Post reported last month that prosecutors had abruptly shifted the investigation from one grand jury to a second and eventually a third after learning that a grand juror on the original panel had leaked information about some of its highly secret proceedings.

The grand jury investigation began following reports in The Washington Post that Treadwell and two other officials of P. I. Properties Inc., a real estate spinoff of Youth Pride, stole, diverted and misappropriated $600,000 from the federal government and from low-income tenants at Clifton Terrace Apartments in Northwest Washington.

Treadwell has denied any wrongdoing. Reached yesterday at the Pride offices, she declined to comment.

The government said in its court filing yesterday that it had consulted with four different lawyers in connection with the subpoenas issued to Treadwell since the investigation began. The government said yesterday it does not know whether Treadwell currently has a lawyer to represent her in the matter.

In November 1979, when the prosecutor's office issued the first subpoena to Treadwell, she was represented by attorney R. Kennieth Mundy. At that time Mundy asked for a timetable to comply with the government's document request and said he would not object to Treadwell's giving the government a handwriting sample. However, a short time later, the government was informed that Mundy was off the case and that Treadwell was then represented by the Washington law firm of Dickstein, Shapiro & Morin. Seymour Glanzer of that firm specifically represented Treadwell.

The following December, Treadwell accepted a subpoena directed to the "Custodian of Records, Youth Pride, Inc." The government said yesterday however that another lawyer, John King, who represented Treadwell in her 1971 divorce from Mayor Marion Barry, said he was the attorney for Youth Pride and that all records were in the custody of Johnny Mickens, chief financial officer for Youth Pride. At King's direction, the government then sought from Treadwell records on Pride-affiliated organizations, according to the court papers.

After several months passed without the delivery of those records, the government, with the agreement of Treadwell's lawyers at Dickstein, Shapiro, issued a new, third subpoena in June 1980 for the records. Over the next several weeks the court filing disclosed yesterday, some 30 boxes of documents were delivered to the courthouse.

Prosecutors had discussed with those lawyers an appearance before the grand jury by Treadwell once the documents were delivered to the prosecutor's office. But, by the time all the documents were received, the firm no longer represented Treadwell, the court records said.

Last October, the government issued a fourth subpoena for Treadwell to appear before the grand jury and submit a handwriting sample. According to the court papers, Treadwell called the prosecutor's office and asked for a delay while she sought another lawyer. The government granted the request.

By Dec. 2, however, there had been no further word from Treadwell or a lawyer, and U.S. Attorney Charles F. C. Ruff wrote a letter to Treadwell insisting on her compliance with the subpoena and threatening a contempt request such as that filed yesterday. The letter was also signed by Assistant U.S. Attorney William D. Pease, who has been supervising the Pride investigation for the prosecutor's office.

Nine days after that letter was sent, another lawyer, Linda Huber of the firm of Tigar & Buffone, called the prosecutor's office, and asked for a delay on the fourth subpoena while Treadwell and that law firm negotiated a representation agreement.

A week later, Huber's office told the government that the firm would not be representing Treadwell. Since then, the government said in its filing yesterday, it has no indication that Treadwell has tried to comply with the subpoena or find another lawyer.

In its court filing, the government said that it felt that it had "demonstrated extraordinary patience and cooperation" with Treadwell over the last 15 months. She has responded, the papers argued, "with a concerted effort to delay and frustrate the grand jury's work," even though, in the view of the prosecutors, Treadwell has no legal basis for noncompliance with the subpoenas.