A long-range plan that sets forth options for future congressional expansion - including as many as 11 major new House and Senate office buildings - has been sharply attacked by two senators.

"This is ridiculous," said Sen. william Proxmire (D-Wis.), an old foe of congressional growth. "I think it's absolutely outrageous . . . Eleven new buildings? How about 535? You need at least one for every member of Congress."

"The only way to hold back Senate growth is to let people suffer in overcrowdedness," said Sen. John H. Chafee (R-R.I.), sponsor of an unsucessful move to curtail construction of the $122 million Philip A. Hart Senate Office Building at Constitution Avenue and Second Street NE.

THe "Master Plan for the Inoted States Capitol" is being prepared simply to identify the best sites and design concepts for future congressional expansion, according to Captiol Archifect George M. White None of the plan's proposals have yet been funded, endorsed or even debated by congress.

Options that White has under consideration include:

Five new Senate office buildings including the Hart building, already under construction just east of the existing Senate office buildings;

Six new Hose office complexes generally clustered to the south of the present Rayburn, Longworth and Cannon builgings;

Courtyard additions to the Longworth and Cannon buildings;

Above and below-ground additions to the Capitol itself;

Nearly 7,000 new parking spaces for congressional employes;

An underground "people mover" connecting Congress to Metro's Blue and Red subway lines;

Eventual creation of a new Supreme Court "enclave" elsewhere in the city , with the present court building turned into a new branch of the Library of Congress.

The combined impact of all projected House and Senate expansion would b to add approximately 6.5 million square feet of space to an existing stock of about 4.9 million square feet.

But the plan, according to White, will make no assumptions about the actual need for any of this space beyond the Hart building and about 1.5 million square feet to cure current House overcrowding.

"An an architect, it seems to me that I have to provide housing for my client in accordance with what I see," said White, explaining that there are not 67 square per congressional employe compared to the desirable 150 square feet per employe.

"No one knows what the future holds," White said. "If the need doesn't exist, you can leave the plan on the shelf."

Critics inside and outside congress expressed displeasure with the emerging outlines of the plan.

Ellen Seidman, cochairperson of a coalition of Capitol Hill civic groups that has been studying congressional expansion plans, charged that White seemed to favor " the more grandoisealternatives" that would involve penetrating the neighboring Capitol Hill historic districts.

"It's our feeling that one of the jobs of the architect is to tell his client that he's asking too much," Seidman said. "He is the technician with the expertise to say what needs are real and what needs are simply wishes."

"The assumption underlying the report is that new buildings are needed," wrote columnist Richard E. Cohen in the current National Journal, a weekly that focuses on politics and government. "There is nodiscussion of retaining roughly the current scale of space."

An interim report issued by White's office last year argued that past increases in congressional staff "have resulted fundamentally from national population growth." Chafee called this explanation "hogwash," pointing out that total U.S. population had gone up about 25 percent in the last 20 years (from about 175 million to nearly 220 million), while congressional employment rose nearly 300 percent.

In a spirited debate on the Senate floor 10 days ago, Chafee described the hart building - with its 16-foot ceilings, $360,000 gym, $1.4 million multimedia hearing room, $3 million in interior marble facings - as "neo-Mussolini" in style. But the Senate defeated chafee's move to call off construction of the building by a vote 45 to 29.