The Defense Department missed a top Republican lawmaker's deadline to provide information about an FBI informant who was a source for the bureau's Trump-Russia investigation during the 2016 election cycle.

Senate Finance Committee Chairman Chuck Grassley wrote to then-acting Defense Secretary Mark Esper earlier this month seeking details about contracts the Defense Department's Office of Net Assessment had with Stefan Halper, a former Republican operative and White House aide who became a foreign policy academic with close ties to both American and British intelligence.

During the 2016 presidential campaign, Halper had discussions with at least three Trump campaign members: foreign policy aides George Papadopoulos and Carter Page as well as Trump campaign co-chairman Sam Clovis. The New York Times reported in April that the Justice Department inspector general was looking into his actions to see if he exceeded the scope of his assignment.

Grassley's letter, which cited concerns about whether the defense contracts "were used to support potential partisan political or other improper or wasteful activities," set a July 25 deadline. And while the Defense Department responded to the Iowa Republican's demand, Grassley's office said the department's response was inadequate.

“Senator Grassley received a response from DoD regarding his request for more information on the steps DoD has taken to address contract oversight and management failures that the DoD IG identified during a review of Stefan Halper’s contracts. DoD’s response failed to address the questions detailed in his original letter. Senator Grassley has reiterated to DoD that they must address all of his questions in writing and provide the requested documentation," Grassley said in a statement shared with the Washington Examiner on Tuesday.

A Defense Department representative confirmed receipt of Grassley's request and told the Washington Examiner, "As with all congressional correspondence, we will respond directly to the request."

Grassley's letter was a follow-up to a Defense Department inspector general audit, which he requested, of $1.05 million worth of contracts with Halper between 2012 and 2018 to complete studies related to Chinese military strategy, China's economy, and "the prospect of Russian-Chinese collaboration against the United States."

Noting how the audit said ONA was unable to provide "sufficient" documentation on Halper's work and travel expenses, which the watchdog found was commonplace for similar contracts, Grassley wrote the audit "revealed significant flaws in ONA’s contract management and oversight process that clearly indicate ONA’s internal controls over taxpayer-funded work are weak or non-existent."

Grassley demanded the Defense Department explain steps taken to address the inspector general's recommendations and ONA to provide a briefing to his committee's staff on the Halper contracts.

Grassley's request for an audit followed a Washington Times report in the fall of 2018 about a Pentagon strategist who was stripped of his security clearance after he complained to superiors about dubious contracts given to Halper. The report said the ONA strategist, Adam Lovinger, was a supporter of President Trump, and in an ethics complaint, his attorney said Lovinger warned his superiors about “sweetheart” deals for Halper and for a “best friend” of Chelsea Clinton, who is the daughter of former President Bill Clinton and 2016 presidential candidate Hillary Clinton.

Halper was the director of American studies in the department of politics and international studies at Cambridge University, where he worked for years alongside Sir Richard Dearlove, who had spent decades with MI6 including as its director from 1999 to 2004.

Christopher Steele, who was hired by the Clinton campaign-funded opposition research firm Fusion GPS and was the author of the Trump dossier used in Foreign Intelligence Surveillance Act applications to target Carter Page, was in MI6 from 1987 until 2009. Dearlove has described Steele as the “go-to person on Russia in the commercial sector” and said his reputation is “superb.” Inspector General Horowitz is investigating allegations of FISA abuse and is expected to release his report after Labor Day.

Halper organized and hosted a series of Cambridge Intelligence Seminars that were attended by intelligence community members, academics, and researchers from around the world. One such seminar in 2014, put together by both Halper and Dearlove, was attended by then-President Barack Obama’s Defense Intelligence Agency Director Michael Flynn, who played a prominent role in the Trump campaign beginning in early 2016 and served a short stint as Trump’s national security adviser in 2017. Halper also reportedly ran into Page at Cambridge in summer 2016.

Dearlove is now listed as the chairman, and Halper is listed as a partner at the Cambridge Security Initiative, which states it “provides a unique link between the worlds of business, government, and academia with unrivaled expertise in security and intelligence issues.”