Outnumbered and outspent by industry, the public is under-represented and often overlooked in proceedings before federal regulatory agencies, according to a major Senate committee report released today.

The unusually critical report, unanimously approved by 14 members of the Senate Government Operations Committee, blames the lack of public participation on the high cost of agency proceedings and administrative obstacles that preclude consumer interest groups at the outset.

"The public's interest versus the private interests before federal regulatory agencies can be likened to the Biblical battle of David and Goliath - except that David rarely wins," Sen. Abraham Ribicoff (D-Conn.), the committee chairman, said in a statement accompanying the report.

The report is the third in a series of volumes to be released this year as part of what Ribicoff has called "the most comprehensive study" of deficiencies in the regulatory process and the steps that should be taken to eliminate them.

A fourth volume also made public today characterized the regulatory process as punctuated by delay and frustration. It said that a survey of about 1,000 eight major commissions cited "undue delay" as the major problem with federal regulation.

"At agency after agency," the report said, "participation by the regulated industry predominates - often overwhelmingly. Organized public interest representation accounts for a very small percentage of participation before federal regulatory agencies.In more than half of the formal proceedings, there appears to be no such participation whatsoever, and virtually none at informal agency proceedings."

"The single greatest obstacle to active public participation," the 162-page report added, "is the lack of financial resources by potential participants to meet the great costs of formal participation."

In some cases, the study said, industry spent as much as 50 to 100 times the resources budgeted by public interest participants. For example, it noted that in 1976 the nation's 11 trunk airlines spent more than $2.8 million on attorneys' fees, while the principal public representative spent about $20,000.

Standards set by the Supreme Court governing who can represent the public in judicial proceedings also are a barrier to citizen participation, the report said. And it criticized the agencies themselves for giving inadequate notice, insufficient time for debate and inadequate attention to complaints.

To achieve greater public participation, the report recommended the establishment of an independent consumer agency to promote consumer interests in regulatory proceedings. It also urged Congress to pay the costs incurred by public groups in licensing, rule- and rate-making hearings.

In addition, the report urged each agency to set up a consumer advocacy office, schedule regional hearings and improve public notification procedures.

In a second, 171-page report on the regulatory process, the committee said the process "takes for too long" and costs taxpayers "tens of millions of dollars" more than it should.

A licensing case takes an average 19 months, the average rate-making case takes 21 months, and the average enforcement action lasts three years, the report said.

These delays, the report said, can be attributed to a variety of chronic ills in the agencies. Among them are weak management, unnecessary layers of review, the excessively judicial nature of regulatory proceedings, and too little effort in enforcing deadlines.