Who in the White House budget office called Rudy Giuliani on an August afternoon, and what did they have to talk about for 13 minutes?

House impeachment investigators were unable to answer either question in their report released Tuesday by Democrats on the Intelligence Committee. But the call — and more than a dozen others and texts between President Donald Trump's personal lawyer and White House numbers — showed up in AT&T and Verizon records obtained by the House.

House Intelligence Committee Chairman Adam Schiff, D-Calif., declined to say how the House obtained the phone records.

It's unclear what legitimate purpose the president's personal lawyer would have to speak at length with the White House Office of Management and Budget. But the revelation is likely to fuel arguments from House Democrats that Giuliani was intimately involved in a scheme to use U.S. taxpayer dollars as leverage to advance Trump's personal political interests.

The flurry of messages and calls between Giuliani and the White House on Aug. 8 came as emissaries worked with Giuliani to try to persuade Ukraine's president to commit publicly to investigating Trump's political opponents.

Only a day earlier, former U.S. envoy for Ukraine negotiations Kurt Volker had texted Giuliani, who had just returned from meeting in Madrid with Andriy Yermak, a top Ukrainian presidential aide. Yermak had been trying to lock down a date for a White House visit by Ukraine's president, Volodymyr Zelenskiy, and Volker asked Giuliani to convey to "the boss" the results of his meeting with Yermak "so we can get a firm date for the visit."

Giuliani and Trump's envoys had been discussing with the Ukrainians a statement that Zelenskiy could deliver — perhaps on camera — in what the U.S. ambassador to the E.U., Gordon Sondland, testified was a "quid pro quo." But so far, Zelenskiy hadn’t delivered the statement.

But while Giuliani and Trump's envoys were discussing with the Ukrainians a statement that Zelenskiy could deliver — perhaps on camera — so far it hadn't happened.

Congress and the public would later learn that by this point, Trump had ordered that $300 million in congressionally approved military aid to Ukraine be put on hold, in what Democrats allege was an effort to extract concessions for personal political gain.

On Aug. 8, the day after Volker's text to Giuliani but weeks before the aid suspension became public — Giuliani's call history shows six text messages between him and a White House number, although House investigators couldn't pinpoint the individual at the White House using that number.

The history also showed Giuliani repeatedly calling the White House Situation Room's switchboard and other White House numbers, mostly for less than a minute each in duration, which may suggest he wasn't able to reach the person he wanted.

One call stands out: A nearly 13-minute call at a number associated with OMB, the office controlled by acting chief of staff Mick Mulvaney that had frozen the aid. Again, House investigators couldn't identify exactly who was on the other end of Giuliani's call.

Late that evening, Giuliani also received several calls from the single-digit caller ID "-1." The calls were interspersed with his calls to various White House numbers, including the Situation Room and the switchboard.

Traditionally, phone calls placed by White House officials from their office phones — including phones used by the president — to numbers outside the White House will have their real caller IDs blocked as part of the White House's security protocols. Often, those calls will show up as unidentified numbers or digits other than a 10-digit phone number.

In a statement sent to NBC News on Wednesday, Giuliani blasted the draft report from House Democrats as ignoring "every due process rights held dear by those who appreciate and value fair adjudication."

"Alexander Hamilton is turning over in his grave at Trinity Church," he added.

The records also show that Lev Parnas, a Giuliani associate, and Rep. Devin Nunes, R-California, the ranking Republican on the Intelligence Committee, were in frequent contact last April, when Giuliani was publicly calling for an investigation of Biden.

Schiff, who sparred with Nunes during the impeachment hearings, said he was going to "reserve comment" on Nunes' appearance in the House report. But he added that, while Trump was "digging up dirt" on Biden, "there may be evidence that there were members of Congress who were complicit in that activity."

Schiff said it may be the role of others to investigate further, but did not elaborate.

Joseph Bondy, a lawyer representing Parnas, said on Twitter that Nunes should have recused himself from the impeachment hearings. Parnas has been providing documents to the Intelligence committee in compliance with a subpoena, the report says.

When asked during an interview with Fox News host Sean Hannity on Tuesday if he ever had contact with Parnas, Nunes said," It's possible."

"I haven't gone through my phone records. I don't recall that name," he said, adding: "I remember the name now because he has been indicted."

Other call records obtained by the House show that on Aug. 9, the day after Giuliani's flurry of calls with the White House, Volker and Giuliani spoke twice by phone. Sondland, who pushed Ukraine for investigations, also called White House numbers twice on that day, including one call for 18 minutes, the records show.

Giuliani's call history with the White House as obtained by the House goes back much further. The report from House Democrats says that on April 25, days after Trump's initial congratulatory call to Zelenskiy, Giuliani spoke to a White House budget office number three times, plus another eight calls with a White House number.

Later the same evening, the State Department called then-Ambassador to the Ukraine Marie Yovanovitch and abruptly called her home because of "concerns" from "up the street" at the White House, according to witness testimony taken during the impeachment hearings.

That same day, Giuliani got a nearly five-minute call from the unknown "-1" number, the records show. Just minutes later, he held a brief, 36-second call with Hannity, whose opinion show had echoed many of Trump's and Giuliani's allegations about Yovanovitch and alleged Ukrainian meddling in 2016.