Worried that the government is listening in on your phone calls? Stay away from Newark, N.J. -- a new report calls it the wiretap leader of the United States. State court judges authorized at least 39 wiretaps last year in Essex County, N.J., where Newark is located -- far more than in any other county listed in the report, which was released last week by the Administrative Office of United States Courts. The report also noted that more than half of all reported wiretaps authorized by various courts last year were in the states of New Jersey and New York. Wiretaps granted by New Jersey courts alone accounted for 31.4 percent of all wiretaps in the United States last year, the office said. New York and New Jersey combined for 54.1 percent of all wiretap orders in the nation. Edwin Stier, director of the New Jersey Division of Criminal Justice, said the extensive use of wiretaps in the state means officials have "maintained a very active, aggressive program to deal with organized crime." "New Jersey has for 10 years now been in the lead in using electronic surveillance nationally," said Stier. During 1980, law enforcement authorities obtained a total of 564 wiretap orders from judges -- 483 from state courts and 81 from federal courts. That was up 2 percent from 1979. "This rise in authorizations reversed a six-year decreasing trend," said the report. "The number of authorizations last year was still 34.7 percent below the 865 wiretap authorizations during calendar year 1973, the record high year." The orders, said the report, ranged in length from one day to 180 days. The longest, which included five extensions of the original order, was for a federal wiretap in eastern Louisiana in which officials overheard 22,673 conversations. For the fifth straight year, said the report, the cost of installing and monitoring a wiretap rose. In 1980, it was up 4.3 percent to $17,146. In the past five years, it said, the cost has risen 146 percent.