A New Jersey firm has filed suit against Smithfield Foods Inc., claiming that the firm did not offer shareholders a fair price when it purchased the Esskay meatpacking plant in Baltimore this fall.

Arlington-based Smithfield, the largest meatpacker in the East, purchased Esskay for about $3.5 million after the beleaguered company said it might have to move to Indianapolis because it could not obtain bank financing for a new processing plant.

Under an agreement proposed in August and approved by stockholders in October, Esskay agreed to give Smithfield 40,000 shares of voting common stock for $20 a share in cash and 60,000 shares of nonvoting common stock for $18 a share in cash.

J. L. Schiffman and Co. Inc. of Jersey City owns some 4,000 shares of Esskay stock and has asked the Baltimore Circuit Court to review the deal. If the court finds Smithfield did not pay the market value of the stock, it will be forced to reimburse Schiffman.

Lawyers for Schiffman said former Esskay owner William G. Hupfeldt took care of himself by getting a good price for his 55 percent stock holdings, and then left the smaller stockholders with a raw deal.

Smithfield officials announced plans last month to close the 127-year-old Esskay plant, putting about 300 employes out of work, despite earlier promises to keep it open.

Production will be shifted to Smithfield's plants in Virginia, North Carolina and Milwaukee because workers at the Baltimore plant did not agree to contract concessions, said Joseph W. Luter III, Smithfield's chairman.

Smithfield had proposed changing a rule that required Esskay to raise a worker's hourly rate during a temporary change of duties. The rule now requires the company to pay the higher wage if a worker making $7.50 an hour is asked to shift to an $8 position. When a worker is temporarily transferred to a lower-paying job, the worker retains his higher wage.

Esskay workers have been asked at least three times since 1979 to make concessions to keep the firm running, according to Thomas Russo, president of Local 27 of the United Food and Commercial Workers Union.