A Fairfax County research firm has been accused of bribing government officials in Bangladesh in an effort to block a rival company from importing 70,000 rhesus monkeys for medical research.

The complaint against Hazelton Laboratories Corp., the world's largest biological testing concern, was contained in a $45 million antitrust lawsuit filed by MOL Enterprises Inc. of Portland, Ore.

In a suit in federal district court in Oregon, MOL said that Hazelton and its subsidiaries conspired to interfere with an exclusive 10-year contract that it held with the Bangladesh government. The suit alleges that Hazelton wanted the monkey contract and intended to gain control of the world's research monkey supply so it could raise prices.

Hazelton, a publicly owned company that reported $44.6 million in revenues last year, declined to discuss the suit. "We have not had an opportunity to review the pleadings that have been filed in the case, so at this time we have no comment," said Kirby Kramer, Halzelton's chairman.

John R. Faust Jr., MOL's attorney, said that his client had signed a contract with Bangladesh in 1977 that gave it exclusive import rights to the country's rhesus monkeys, a species widely used in research. The following year, Bangladesh became the only source of the animals after India banned their export. In early 1979, Faust said Bangladesh voided the agreement with MOL.

Faust said yesterday that MOL alleges in its suit that Hazelton had met with a group of unspecified other entities in Beaverton, Ore., in April 1978 to form a conspiracy against MOL. He said MOL, a firm owned by a former zoo veterinarian and two trade show promoters, alleges that the conspiracy led Hazelton to bribe to Bangladesh officials, killing the contract.