Rudy Giuliani
Rudy GiulianiReuters

Federal prosecutors in Brooklyn have been investigating whether several Ukrainian officials helped orchestrate a wide-ranging plan to meddle in the 2020 presidential campaign, including using attorney Rudy Giuliani to spread misleading claims about President Joe Biden and tilt the election in former President Donald Trump’s favor, people with knowledge of the matter told The New York Times on Thursday.

The criminal investigation, which began during the final months of the Trump administration and has not been previously reported, underscores the federal government’s increasingly aggressive approach toward rooting out foreign interference in American electoral politics.

Much of that effort is focused on Russian intelligence, which has suspected ties to at least one of the Ukrainians now under investigation, according to the report.

The investigation is unfolding separately from a long-running federal inquiry in Manhattan that is aimed at Giuliani. While the two investigations have a similar cast of characters and overlap in some ways, Giuliani is not a subject of the Brooklyn investigation, the sources said.

Instead, the Brooklyn prosecutors, along with the F.B.I., are focused on current and former Ukrainian officials suspected of trying to influence the election by spreading unsubstantiated claims of corruption about Biden through a number of channels, including Giuliani, according to The New York Times.

It is unclear whether the Brooklyn prosecutors will ultimately charge any of the Ukrainians.

At one point in the investigation, authorities examined a trip Giuliani took to Europe in December 2019, when he met with several Ukrainians, according to the sources, who spoke on the condition of anonymity to discuss an ongoing inquiry.

At least one of the current and former officials Giuliani met, a Ukrainian member of parliament named Andriy Derkach, is now a focus of the Brooklyn investigation, the people said.

According to the sources, the trip was the culmination of a yearlong effort by Giuliani, with support from Trump, to undermine Biden’s presidential campaign. The effort proceeded primarily on two parallel tracks: collecting information from Ukraine to attack Biden’s diplomatic efforts there as vice president, and pressing Ukraine to announce investigations into Biden and other Trump critics.

The effort ultimately backfired.

Giuliani’s lawyer defended the search for information about Biden, disputing that he relied on misleading information.

“When you investigate allegations of corruption, you talk to all sorts of people; some are credible, and some are not,” the lawyer, Robert J. Costello, said. He added that “some day the truth will come out” about Biden’s dealings in Ukraine.

A spokesman for the United States attorney’s office in Brooklyn declined to comment, as did spokesmen for the United States attorney’s office in Manhattan and the F.B.I.