The House select committee investigating the Jan. 6 Capitol attack issued a subpoena on Wednesday to Peter Navarro, who served as former President Donald Trump’s trade advisor.

In his memoir, Navarro wrote that he worked with Trump ally Steve Bannon to come up with a plan to contest the results of the 2020 election, delaying the certification of the Electoral College vote. MSNBC’s Ari Melber followed up on this during an interview in January, and Navarro explained that the plan was called the “Green Bay Sweep,” and more than 100 lawmakers were on board to “challenge the results of the election in six battleground states” won by President Biden.

The plan was “perfect,” Navarro said in an interview with The Daily Beast, adding that it “all predicated on peace and calm on Capitol Hill. We didn’t even need any protesters, because we had over 100 congressmen committed to it.”

The House select committee’s chair, Rep. Bennie Thompson (D-Miss.), said on Wednesday that Navarro “appears to have information directly relevant” to the panel’s “investigation into the causes of the Jan. 6th attack on the Capitol. He hasn’t been shy about his role in efforts to overturn the results of the 2020 election and has even discussed the former president’s support for those plans.” So far, more than 500 witnesses “have provided information in our investigation,” Thompson added, “and we expect Mr. Navarro to do so as well.”

In a statement to ABC News about the subpoena, Navarro said Trump “has invoked executive privilege, and it is not my privilege to waive. They should negotiate any waiver of the privilege with the president and his attorneys directly, not through me.” He also declared that “the last three people on God’s good earth who wanted chaos and violence on Capitol Hill were President Trump, Steve Bannon, and I.”