Former Senate Intelligence Committee Security Director James Wolfe pleaded guilty to one count of lying about contacts with journalists, in a leak case which saw the Trump administration seizing reporters' private records

A US Senate staffer arrested this year over alleged leaks of classified information to his reporter girlfriend, pleaded guilty Monday to lying to FBI agents.

The Justice Department said James Wolfe, former director of security for the Senate Intelligence Committee, pleaded guilty to one count of making a false statement to agents.

Wolfe, 57, admitted to lying about having had contacts with reporters, including one, later identified as reporter Ali Watkins, who he was having an affair with.

In a plea statement, the Justice Department said Wolfe, without authorization, divulged sensitive "non-public" but not classified information to the reporters.

He faces up to six months in prison and a fine of up to $9,500.

Wolfe was arrested on June 7 as the Trump administration pressed a crackdown on leaks to the media.

According to reports, the Justice Department is pursuing at least 20 separate leak investigations.

"The attorney general has stated that investigations and prosecutions of unauthorized disclosure of controlled information are a priority of the Department of Justice," said Assistant Attorney General John Demers.

As part of the probe, the Justice Department seized years of records related to two email accounts and a phone number belonging to Watkins, the first known case of a journalist's records being seized under the Trump administration.

The Committee to Protect Journalists and other media groups branded the seizure a threat to press freedom.

Watkins, 26, had an affair with the married Wolfe over three years, a period during which she scored repeated national security-related scoops that eventually earned her a job at the end of last year at The New York Times.

The indictment indicated the leaks investigators had focused on took place before she joined the Times.

After Wolfe was arrested, the Times reassigned Watkins to a different beat following an internal review.