(FILES) In this file photo Lawyer of the US president Rudy Giuliani looks on before the US president announces his Supreme Court nominee in the East Room of the White House on July 9, 2018 in Washington, DC.Saul Loeb | AFP | Getty ImagesThe House Intelligence Committee has subpoenaed President Donald Trump’s personal attorney Rudy Giuliani for documents as part of its impeachment inquiry into the president.In a letter to Giuliani dated Monday, the heads of three House committees asked for information related to the president’s and his lawyer’s efforts to get Ukraine’s government to investigate the Biden family. Three Democratic-led panels — the Intelligence, Oversight and Foreign Affairs committees — are demanding that Giuliani produce all text messages, phone records and other communications related to the “scheme” he is accused of perpetrating “in order to determine the full extent of this effort by the President and his Administration to press Ukraine to interfere in our 2020 presidential election.”They wrote that the House Democrats’ probe “includes an investigation of credible allegations that [Giuliani] acted as an agent of the President in a scheme to advance his personal political interests by abusing the power of the Office of the President.” Reps. Adam Schiff, D-Calif., Elijah Cummings, D-Md., and Eliot Engel, D-N.Y. — who lead the Intelligence, Oversight and Foreign Affairs committees, respectively — asked him to produce documents by Oct. 15.Spokespeople for Giuliani and the White House did not immediately respond to CNBC’s requests for comment. Giuliani has suggested he may not comply with committee requests. On Sunday, he told ABC that he “wouldn’t cooperate” with Schiff as long as he leads the panel.The subpoena adds to the heightened scrutiny of both administration officials and outside Trump confidants after the House decided last week to move forward with impeachment proceedings. On Friday, the Intelligence Committee subpoenaed Secretary of State Mike Pompeo for documents. The heads of the Appropriations and Budget committees also asked Friday for records related to the Office of Management and Budget’s involvement in the Trump administration deciding to hold back nearly $400 million in military aid to Ukraine.Lawmakers are investigating whether the president abused the power of his office to influence the 2020 election by pushing Ukraine to investigate Hunter Biden, son of former Vice President Joe Biden. The elder Biden is one of Trump’s chief rivals for the presidency next year. The intelligence community whistleblower complaint at the center of the impeachment inquiry also alleges a White House effort to cover up records of a July 25 phone call during which Trump asked Ukrainian President Volodymyr Zelensky to “look into” the Biden family.A summary of the conversation between the leaders, the whistleblower complaint released by the administration last week and Giuliani’s own comments suggest the president’s attorney played a major role in efforts to get Ukraine to investigate the Bidens. When discussing the Biden family with Zelensky, Trump mentioned that he would like Giuliani to call the Ukrainian president.The whistleblower’s complaint, meanwhile, called Giuliani a “central figure” in the effort to influence Ukraine’s government. The person writes that Giuliani met with one of Zelensky’s advisors in Madrid in August in what was described as a “direct follow-up” to the call between Trump and his Ukrainian counterpart.Giuliani has talked personally about his involvement in efforts to sway the Ukrainian government. When asked by CNN earlier this month if he asked Ukraine to look into Joe Biden, he responded, “Of course I did.”He also shared a text message he received from the administration’s former special envoy to Ukraine, Kurt Volker. After having breakfast with Giuliani, Volker said he was connecting the president’s attorney with Andrey Yermak, whom he described as being “very close to President Zelensky.” Volker resigned from the post on Friday.The committees on Monday asked Giuliani to produce documents related to Hunter Biden and any efforts to urge Ukrainian officials to investigate Burisma, the Ukrainian energy company on whose board the younger Biden held a seat. They also asked for information on meetings between administration officials and Ukrainian representatives and records about U.S. foreign assistance to Ukraine, among other topics.Schiff, Cummings and Engel wrote that Giuliani’s “failure or refusal to comply with the subpoena, including at the direction or behest of the President or the White House, shall constitute evidence of obstruction of the House’s impeachment inquiry and may be used as an adverse inference against you and the president.”— CNBC’s Kevin Breuninger contributed to this report.