An irate shareholder of CACI International Inc., an Arlington defense contractor, has sued the company's officers and directors because they rejected a $4.50-a-share buyout offer from a local group.

The suit was filed by Larry Pfirman, president of Tara Lee Sportswear Inc. of New Berlin, Pa., who owns 701,000 shares, or 7 percent of CACI's stock.

Pfirman charged that the CACI board failed to properly consider a recent buyout offer from LHN Group of Alexandria. At the time of the LHN offer, CACI stock was trading at under $3 a share.

The suit said CACI officials had refused to consider "a bona fide offer for the company at a substantial premium over market price" and were "in abrogation of their fundamental fiduciary duties to seek the best possible transaction for the shareholders."

The suit is part of an unusual period of tension between the executives and shareholders of the 29-year-old company.

The problems surfaced after the death last April of the firm's chairman and co-founder, Herbert W. Karr. He controlled the company under a dual-class stock plan but had arranged for the company to shift back to a single-class share plan over several years.

Pfirman's suit was directed at CACI Chairman J.P. "Jack" London and five members of the board of directors.

The suit charged that CACI officials had "carried out a preconceived plan and scheme to place their own personal interests ahead of the interests of CACI and its public shareholders and thereby entrench themselves in their offices and positions within the company."

John H. Baker, executive vice president of CACI, said, "The board is confident it has acted in the best interests of the company and its shareholders generally and is confident that its actions will be upheld."

The suit, filed in U.S. District Court here, names directors John DeNigris, Thomas H. Moorer, Paul J. Coleman, J. H. Berkson and Warren R. Phillip, in addition to London and Baker.

The LHN Group partners are Michael S. Luther, a West Coast investment banker; Elliot Needleman, an executive of S.T. Research Corp. in Newington, Va.; and Thomas G. Hotz, a commercial leasing representative at Julien J. Studley Inc. in McLean.

Hotz, on an earlier occasion, said LHN represented an equity investment group, which he declined to name. He also said LHN was interested only in a friendly deal and would have the financing available if CACI were interested.

CACI's sales for its fiscal year ended June 30 were about $148 million, with 70 percent of its computer services work done for the federal government. It employs about 2,500 people.

In the last three fiscal years, the company's profits have been flat, in part because of a slowdown in the awarding of government contracts.