The Peace Corps, in its 20th anniversary year, is at the center of an increasingly bitter administration battle over its independence and its budget, a battle that officials say could damage its work overseas.

The corps is under strong attack from hard-line conservative groups with access to high administration officials, and at the same time is facing budget cuts that could reduce the number of volunteers going abroad.

As a result, according to well-placed sources in the Peace Corps, Director Loret Ruppe is spending valuable time defending the corps' work and countering accusations from the far right that it is "anti-Reagan." The effect, the sources said, has been to reduce morale among full-time officials and to discourage prospective volunteers.

Much of the irritation among Peace Corps workers is directed at staff members of the Action agency, which is linked administratively to the corps. Although an executive order by President Carter in May, 1979, guaranteed autonomy for the Peace Corps, with only some shared support services, the two organizations share the same building and there are close management links.

According to one Peace Corps official, there is constant friction between the staffs, leading to such incidents as the appearance on walls and elevators in the Action offices of copies of an article highly critical of the Peace Corps that appeared in the conservative publication "Human Events."

The article attacked the corps' 20th anniversary celebration in June, which it claimed became a forum for "virtually every anti-Reagan freak around." The Peace Corps was described in the article as "a dangerously anti-Reagan instrument."

The accusations caused considerable distress in the Peace Corps, because they were considered unfounded and because copies were known to have been circulated at the White House. Ruppe, according to officials close to her, was outraged by the article.

She is reportedly convinced of President Reagan's support for the Peace Corps but dismayed by conservative attacks on her, because she believes that the work of the corps in the Third World should be attractive to those who profess to believe in "self-help."

The main focus of the anti-Peace Corps campaign is legislation to separate the corps completely from Action. That move is opposed by the administration, on the grounds that it would cost about $3 million a year more to run separate organizations. The bill, passed by the Senate, faces some House opposition, but a congressional staff source said Friday that the bill is expected to become law.

It was introduced in the Senate earlier this year as part of the campaign by liberals to block the nomination of Thomas Pauken as head of Action. One of the arguments used against Pauken, a Republican congressional candidate in Texas last year, was that his connection with military intelligence in Vietnam would be damaging to the Peace Corps, because it would provide opportunities for the Soviet Union to charge volunteers with intelligence links.

As a result of the controversy surrounding his nomination, and his reputation as a hard-line conservative, Pauken is regarded warily by many Peace Corps officials, and the friction with Action staff has tended to confirm their initial fears, according to sources in the corps, despite an apparently good working relationship between Pauken and Ruppe.

Pauken has made it clear that one of his main aims as Action director is to launch an assault on the VISTA program, established in the 1960s to help depressed areas in the United States by organizing teams of volunteers to advise on various topics.

However, what concerns some Peace Corps staff members is that Pauken, who has publicly expressed support for the corps, is closely associated with some of the far right groups now calling for it to be brought under stricter control.

On June 19, for example, Pauken addressed a meeting of the Kingston Group, a private discussion group set up by several conservative organizations, including the Conservative Caucus and the Committee for the Survival of a Free Congress, which meets regularly in the back room of a private house on Capitol Hill.

During this meeting an 11-page list of VISTA programs was circulated. According to a participant at the meeting, the list was handed out by Pauken, who said the programs were "leftist" and were to be dissolved.

Pauken denied in an interview that he had handed out any list at the meeting, but said his staff might have done so. He said the Action staff was examining individual programs to see if they fulfilled the criteria laid down for the agency.

One of the participants at the Kingston Group meeting, who was invited as part of a Conservative Progress Briefing in Washington, described the session as "a shock" because of the passionate antagonism to federal programs displayed and the intolerance to anyone not associated with the far right.

The open hostility of some Action officials to the Peace Corps is causing fears that this year's budget cuts may be the prelude to a more severe cutback. The 1982 appropriation has dropped to $95 million, from $106 million in fiscal 1981, and activities are expected to be concentrated in fewer countries. By 1983 the number of volunteers is expected to be about 20 percent below the figure planned for 1982 by the Carter administration. There are currently 5,400 volunteers in 60 countries.

Yet Ruppe and her staff are convinced that the Peace Corps delivers a large benefit to the nation, at a relatively small cost. One report from a senior official now circulating in the office describes a lengthy tour to African countries where volunteers are at work and concludes: "The United States does not yet realize the incredible impact that the Peace Corps has on these smaller nations--an incredible impact on their societies, world outlook, identities and conceptualization of the West."

Tuesday is the 20th anniversary of the signing of the Peace Corps Act, and an atmosphere of celebration might be expected. But instead, many officials are frustrated and distressed by the attacks which are forcing them to spend time on defensive bureaucratic maneuvers and which they believe could discourage volunteers. They are also concerned that President Reagan's support for the corps might be undermined by hard-liners who regard it as an unpleasant vestige of Kennedy liberalism.

As a result, Peace Corps officials believe they may even be facing a battle for survival.