NEW ORLEANS — The Justice Department will escalate its crackdown on illegal foreign influence operations in the United States, a senior Justice Department official said Wednesday, violations that prosecutors have targeted with renewed vigor in recent years.

Prosecutors plan to pursue more cases of covert foreign influence, John C. Demers, the head of the Justice Department’s national security division, said at a conference in New Orleans on white-collar fraud.

The move, one of the first significant initiatives under Attorney General William Barr, shows that the Justice Department has made a priority of one of the targets pursued by special counsel Robert Mueller: potential violations of the Foreign Agents Registration Act, or FARA, which requires lobbyists and others to disclose any work they do to further the interests of foreign governments. Prosecutors had for decades mostly ignored such violations as lobbyists accepted millions of dollars from other nations.

Demers said that the department was overhauling its FARA enforcement unit and would assign Brandon L. Van Grack, a former prosecutor on Mueller’s team and a deputy chief in the national security division’s counterespionage unit, to oversee it. The new role shows that the department has shifted “from treating FARA as an administrative obligation and regulatory obligation to one that is increasingly an enforcement priority,” Demers said.

Van Grack was involved in some of the special counsel’s most high-profile prosecutions, including the cases against Paul Manafort and Michael Flynn, former top aides to President Donald Trump.

The lobbying world had long been dismissive of the threat of prosecutions related to foreign influence or violations of FARA. For nearly a half-century, from 1966 until 2015, the Justice Department pursued only seven FARA cases, the department’s inspector general said in a report.

Van Grack temporarily left the Justice Department’s national security division to work with Mueller’s team, returning to his previous post in August after working on the indictments of Flynn, who pleaded guilty in late 2017 to lying to investigators, and Manafort. Manafort is due to be sentenced Thursday in Northern Virginia on a conviction of financial crimes in a case that stemmed from his consulting work for a former pro-Russian president of Ukraine. During that trial, an unsavory picture emerged of the lawyers and consultants who netted big paydays for their work on behalf of foreign governments.

The abrupt end to Manafort’s career, which included work with foreign clients who wanted a say in U.S. politics, had a chilling effect on the lobbying world.

As it delved into the work that occurs on behalf of foreign governments in the lobbying world, the special counsel’s office also investigated lawyers and lobbyists who worked on behalf of Ukranian entities, including Gregory B. Craig, the White House counsel under President Barack Obama and a lawyer for the firm Skadden, Arps, Slate, Meagher & Flom.

In January, the law firm paid $4.6 million to settle a Justice Department investigation into whether its Ukraine-related work violated lobbying laws.

This article originally appeared in The New York Times.