The Reagan administration yesterday proposed stiff new regulations designed to prevent federal contractors and grant recipients--everyone from weapons manufacturers to nonprofit health organizations--from using federal funds for "political advocacy."

Under the proposals, organizations could not conduct political activities from the same building used for their federally funded work. A copying machine paid for in part with federal funds could not be used to duplicate a petition to a city council. No official, even one who receives only a portion of his salary from federal funds, could engage in political activities, except on his own time.

At the same time, the proposals would broaden the definition of political advocacy significantly.

Office of Management and Budget officials yesterday took pains to say that the rules will fall equally on all groups, both aircraft manufacturers lobbying for the B1 bomber and health organizations fighting abortion-related restrictions.

But Nan Aron, executive director of the Alliance for Justice, a coalition of public interest groups, disagreed. "The military establishment has the resources to carry the overhead for this kind of activity," to rent another building for lobbying staff, she said.

"The public interest groups--the Urban Leagues, the Jesse Jacksons, the environmental groups, do not. It's nothing more than a cynical effort to hit the liberal groups."

"It is a distortion of the marketplace of ideas for the government to use its financial power" for political purposes, said an OMB statement issued yesterday. Officials said the rules would not bar anyone from doing anything on his own time or with his own money.

Anne Steinberg, a Washington lawyer for many nonprofit groups, said the proposals "look like a major change in policy that is quite significant, a very serious change."

Use of federal funds for political purposes has always been prohibited. But officials said that complicated and inadequate regulations and auditing procedures sometimes defeated the purpose of the ban. For example, an organization getting federal money and private money could help finance a political rally and simply say it used the private money.

Under the new proposal, if 5 percent or more of a building rented or built with some federal funds were ever used for political purposes, the federal funds for the building would be withdrawn. For serious violations, the recipient could be barred from receiving further federal money.

The regulations also ban recipients from "inducing" or "coercing" employes to become involved in advocacy and bar the use of federal money for paying dues to political organizations or buying subscriptions to their publications.

Among the things the OMB would consider as advocacy would be political campaigns, attempts to influence government decisions by appeals to public opinion or "communication" with elected or appointed officials, and participating in litigation as a "friend of the court." Steinberg said the definition could be read to include participation in federal rule-making proceedings.

Controversies have arisen in the past few years over the political activities of contractors--such as organizing employes to lobby for lucrative military projects--and nonprofit organizations. Conservatives last year launched a campaign against "liberal and left-leaning" organizations that receive federal funds.

The rule changes for the nonprofit groups will be proposed next week in the Federal Register. The revisions for the contractors will be handled separately by the Defense Department, the General Services Administration and NASA.