The Securities and Exchange Commission said last night it has settled its stock fraud charges against First Jersey Securities Inc. under an agreement that appoints a special consultant to make sure the firm complies with securities laws.

The SEC had filed a civil suit in 1983 charging First Jersey and its president, Robert E. Brennan, with manipulating stock prices and was conducting another investigation into other complaints of stock fraud.

Both sides hailed the outcome. SEC Regional Administrator Ira Lee Sorkin said that, because of the appointment of a special consultant, who has the authority to make changes in First Jersey's sales techniques and business practices, the SEC fared better with the consent decree than it would have had the cases gone to trial.

The consultant, Alan R. Bromberg, an expert in securities law at Southern Methodist University in Texas, will monitor First Jersey for at least 1 1/2 years and report to U.S. District Judge Milton Pollack, who signed the consent decree.

Sorkin also said the agreement enjoins the company and Brennan from engaging in stock manipulation or securities fraud. Any violation of the permanent injunction can be punished by a criminal contempt charge, Sorkin said.

First Jersey, however, said the agreement "vindicates" it and Brennan, who has been publicly identified with the fast-growing firm through his prominent role as spokesman in its prime-time television commercials.

"There was no finding of any wrongdoing by First Jersey or any of its employes," the company said in a press release that was distributed to reporters at the federal court in Manhattan while SEC officials were going to Pollack's home to get the consent decree signed.

"There has never been a single finding by the SEC or by any court that I or First Jersey have ever violated any securities law because we never have violated any securities law . . . and certainly intend to continue our compliance with the law in the future," Brennan said.

In its release, the SEC said the agreement was signed by First Jersey "without admitting or denying the commission's allegations."

The SEC has conducted two major investigations of First Jersey's stock-selling techniques, with one probe culminating in the filing in January 1983 of a civil lawsuit against the company, Brennan and two top executives. They were accused of making more than $3 million by artificially inflating the price of shares in Geosearch Inc., a small oil and gas company.

Other complaints under investigation by the SEC dated to 1979 and centered on First Jersey's trading in stocks in several companies in which it was a market maker as well as a broker. All those issues were dropped by the agreement.

The appointment of a special consultant with broad powers to monitor the company is an unusual step in settling an SEC stock fraud investigation. Bromberg is empowered to make sure that First Jersey's sales practices, business operations and supervisory procedures comply with securities laws, SEC regulations and the guidelines of the securities industry's self-regulation organizations. The agreement gives him 90 days to recommend changes in First Jersey's operation, if needed, to bring it into compliance with the law. Pollack can order the company to adopt his recommendations.

Within one year, First Jersey is required to swear to the court that it is following Bromberg's recommendations. Under the decree, Bromberg will conduct another review for the court six months later.

First Jersey has taken an extremely hard line in fighting the SEC probes, taking the commission to court on procedural moves and in 1982 accusing the SEC of losing 22,000 pages of records that were necessary for its defense.

"The battling and litigating with the SEC was extremely costly but absolutely worth it," Brennan said last night.

Brennan started First Jersey in 1974, specializing in the sale of little-known stocks to small individual investors. In the past 10 years, it has grown from an operation with five employes to one that has 1,200 people serving 500,000 customers.

A good part of that growth has been the result of its aggressive television advertising campaign, in which Brennan appears near landmarks such as the U.S. Capitol and the Grand Coulee Dam.