An 800-page report to be released on Thursday by House investigators will conclude that Donald Trump criminally plotted to overturn his 2020 election defeat and “provoked his supporters to violence” at the Capitol with false claims of widespread voter fraud.

The resulting 6 January 2021 insurrection by Trump’s followers threatened democracy with “horrific” brutality toward law enforcement and “put the lives of American lawmakers at risk”, according to the report’s executive summary.

“The central cause of January 6th was one man, former President Donald Trump, who many others followed,” reads the report from the House January 6 committee, which is expected to be released in full on Thursday. “None of the events of January 6th would have happened without him.”

Before the report’s release, the committee released 34 transcripts on Wednesday evening from the 1,000 interviews it conducted over the last 18 months. Most of those released feature witnesses who invoked their fifth amendment right against self-incrimination.

The report’s eight chapters will largely mirror nine hearings this year that presented evidence from the private interviews and millions of pages of documents. They tell the story of Trump’s extraordinary and unprecedented campaign to overturn his defeat and his pressure campaign on state officials, the justice department, members of Congress and his own vice-president to change the vote.

A 154-page summary of the report released on Monday details how Trump amplified the false claims on social media and in public appearances, encouraging his supporters to travel to Washington and protest Joe Biden’s presidential election win. It also addresses how the then president urged supporters to “fight like hell” at a huge rally in front of the White House that morning and then did little to stop the violence as they beat police, broke into the Capitol and sent lawmakers running for their lives.

It was a “multi-part conspiracy”, the committee concludes.

The report comes as Trump is running again for the presidency and facing multiple federal investigations, including inquiries into his role in the insurrection and the presence of classified documents at his Florida estate. A House committee is expected to release his tax returns in the coming days – documents he has fought for years to keep private. And he has been blamed by Republicans for a worse-than-expected showing in the midterm elections, leaving him in his most politically vulnerable state since he won the 2016 election.

It is also a culmination of four years of work by a House Democratic majority that has spent much of its time and energy investigating Trump and that is ceding power to Republicans in two weeks. Democrats impeached Trump twice – both times he was acquitted by the Senate – and investigated his finances, his businesses, his foreign ties and his family.

But the January 6 investigation has been the most personal for the lawmakers, most of whom were in the Capitol when Trump’s supporters stormed the building and interrupted the certification of Biden’s victory.

“This committee is nearing the end of its work, but as a country we remain in strange and uncharted waters,” said the panel’s chairman, the Democrat Bennie Thompson of Mississippi, at the meeting on Monday to adopt the report and recommend criminal charges against Trump. “We’ve never had a president of the United States stir up a violent attempt to block the transfer of power. I believe nearly two years later, this is still a time of reflection and reckoning.”

The transcripts released on Wednesday include interviews with Jeffrey Clark, a senior official in the Trump justice department who worked to advance Trump’s efforts to overturn the election, and John Eastman, a conservative lawyer and an architect of Trump’s last-ditch efforts to stay in office. Each invoked his fifth amendment right against self-incrimination.

Also included in the release is testimony from witnesses associated with extremist groups that were involved in planning before the attack. The Oath Keepers founder, Stewart Rhodes, who was convicted last month of seditious conspiracy for his role in the planning, and the former Proud Boys leader Enrique Tarrio both spoke to the committee. Tarrio and four other members of the extremist group are in court on similar charges this month.