Ten major government contractors billed to the taxpayers more than $2 million in lobbying expenses in a two-year period, according to an audit that the Pentagon fought for years to keep closed.

The results of the audit, conducted at the contractors' Washington offices in 1974 and 1975, were disclosed yesterday by Common Cause, which obtained the documents under a Freedom of Information Act request after a four-year court battle.

The citizens' lobbying organization said the purpose of the Washington offices is "to grease the connections and ease the way for multibillion-dollar sales," and said the sums involved must be much larger than $2 million because there are "hundreds of defense contractors."

What action was taken on the findings of the audits, conducted by the Defense Contract Audit Agency (DCAA), is not known to Common Cause.

The organization reported the findings in an article in its magazine by editor Florence Graves, who cited these highlights of the two-year period:

Martin Marietta's Washington office claimed expenses of $181,861, including the salary of its director, K.K. Bigelow. The DCAA judged them "unallowable" in their entirely because they paid for activities "concerned with influencing legislation," such as building "rapport with congressmen from the 35 states in which Martin has divisions . . . . " The items also included $24,000 paid as "consultant retainer fees" to retired Army Gen. W.W. Quinn. The DCAA found the payments to Quinn "unallowable since his services are primarily related to lobbying." The company said it doesn't lobby.

Rockwell International made a film called "The Threat, What Can We Do?" that, the audit said "furthers the image of the B1 bomber program." The company billed the taxpayers $17,185 for 100 prints.

Sperry Nivac asked reimbursement of $120,000 in salary, entertainment and related expenses for its public relations and sales promotion manager "who, in effect, was a lobbyist," the audit said.

Hughes Aircraft claimed $42,976 for a condomimium in the Shoreham apartments. In 1974, it asked reimbursement for $4,783 for entertainment supplies and services including silverware, linens, bartender, reception and limousine services, and $1,308 for furnishings and decorations in a "sky suite" at the Capital Centre.

* Raytheon Co. claimed, over 21 months, $8,516 for lodging, meals and guides for Maryland goose hunts for employes and unidentified guests.

General Dynamics sought reimbursement of $7,350 for tie tacks and models of F16 and F111 fighter aircraft.

Lockheed Aircraft charged $22,032 in first-class air fare and other travel expenses for persons -- including spouses -- attending the Farnborough and Paris air shows.

* The other firms audited were Boeing, Collins Radio Group and Sperry Rand.

Graves wrote that the Pentagon has no regulation specifically permitting charging of lobbying costs to the taxpayers, and, in fact, has never defined "lobbying." She also said that the auditors "met a consistent pattern of stonewalling" by the companies.

The study comes two months after the Council on Economic Priorities, in a wide-ranging 465-page report called "The Iron Triangle," revealed that the Washington offices of five companies spent nearly $16.8 million for government relations activities between 1974 and 1975. They initially charged all but $1 million to their contracts although "a substantial portion . . . were for lobbying activity," the report said. Rockwell made the largest outlay, $7,048,000, followed by Boeing at $3,629,000; General Dynamics at $2,777,000; Lockheed Aircraft, $2,739,000; and Grumman, $560,000.