The Justice Department filed suit yesterday against the state of New Jersey and 12 of its largest cities, charging them with discriminating against blacks and Hispanics who applied for jobs as firefighters.

The suit which is unusual because it asks for statewide remedies, alleges that the state civil service examiner and the cities have traditionally failed to recruit, hire and promote blacks and Spanish-surnamed persons on an equal basis with whites.

Justice claims in the suit that the state-administered hiring examination is not job related and has a "detrimental impact" on minorities, a department spokesman said.

Named as defendants are the state, state civil service examiner Ralph P. Shaw and the cities of Atlantic City, Camden, East Orange, Elizabeth, Hoboken, Jersey City, New Brunswick, Newark, Passiac, Patterson, Plainfield and Trenton.

The department spokesman noted that the 12 cities have 3,800 uniformed firefighters to serve a combined population of 1.4 million. Though 34 per cent of that combined population is black and 6 per cent Hispanic, only 4.2 per cent of the firefighters are black and only 0.2 per cent are Hispanic.

The suit asks that the state and cities be required to award back pay and seniority to job applicants and employees who have been discriminated against, and that they be required to adopt goals and timetables for hiring blacks and Hispanics to overcome past discrimination.

Officials for the state of New Jersey could not be reached yesterday for comment.

The New Jersey discrimination suit is the second statewide action filed by the Justice Department in recent months. In June, 23 Louisiana cities agreed to hire more blacks and women for their police and fire departments after a similiar suit was filed.

Gerald F. George, a Justice Department attorney, who worked on both the Louisiana and New Jersey suits, said in a telephone interview from Newark yesterday that the recent actions did not signify a rash of such statewide actions against public employers.

He noted that the suits against the two states' hiring practices were possible because they used a system where a state examiner administers civil service tests for all city police and five departments.

George declined comment on whether future action is likely against New Jersey police departments. He said that none of the cities involved has agreed to consent decrees, but "we're talking."

The goal of any such agreement would be for the cities to hire blacks and Hispanics in proportion to their numbers in each city's work force, George said.