Lawmakers investigating the assault on the US Capitol voted unanimously Monday to pursue criminal contempt charges against Donald Trump's former chief of staff for refusing to testify.

Mark Meadows has made clear he has no intention of complying with a subpoena to appear before the cross-party January 6 congressional select committee and missed a scheduled deposition for the second time last week.

Members are investigating Trump's efforts to overturn his defeat in the 2020 presidential election through an anti-democratic campaign that led to the deadly Capitol riot -- and the help he got from Meadows.

Trump's fourth and final White House chief -- a former congressman -- told the panel he would withhold testimony until courts resolve his former boss's claim of "executive privilege," which allows presidents to keep certain conversations with aides private.

"Whatever legacy he thought he left in the House, this is his legacy now: former colleagues singling him out for criminal prosecution because he wouldn't answer questions about what he knows about a brutal attack on our democracy," committee chairman Bennie Thompson said.

"That's his legacy. But he hasn't left us any choice. Mr. Meadows put himself in this situation. He must now accept the consequences."

White House Chief of Staff Mark Meadows failed twice to appear for a deposition
The Justice Department will now decide whether it will prosecute Mark Meadows. AFP / Brendan Smialowski

Investigators maintain Meadows has undermined any right to refuse testimony, as the ultra-conservative is promoting a new memoir that includes detailed accounts of January 6 and his conversations with Trump.

He has also spoken numerous times about the attack in primetime appearances on right-wing cable network Fox News.

Many of the questions the committee wants to ask him concern 6,600 pages of records taken from personal email accounts and about 2,000 text messages that he turned over before he stopped cooperating, without claiming any privilege.

An appeals court last week rejected Trump's effort to stop the committee accessing documents and testimony from former White House aides, agreeing with a lower court that the defeated ex-president had provided no reason for secrecy. He was given two weeks to appeal.

Meadows was Trump's most senior aide at the time of the assault and was reportedly with the then-president in the White House as the rioters breached the Capitol.

US Representative Adam Schiff says Meadows will not be able to sustain his defense defying his subpoena
US Representative Adam Schiff says Meadows will not be able to sustain his defense defying his subpoena AFP / MANDEL NGAN

The committee says he is "uniquely situated to provide key information, having straddled an official role in the White House and unofficial role related to Mr. Trump's re-election campaign."

The probe released a 51-page document Sunday describing some of Meadows' communications, including a January 5 email in which he told an unidentified person the National Guard was on standby to "protect pro-Trump people."

The cache included "panicked messages" to Meadows from administration officials during the assault, panel member Adam Schiff said.

Donald Trump Jr. and "multiple Fox News hosts" also reached out, urging him to get the president to call off the rioters, committee deputy chair Liz Cheney revealed.

The committee will green-light the contempt citation Monday evening and the Democratic-controlled House of Representatives is expected to vote Tuesday to refer Meadows to the Justice Department.

A timetable for a charging decision has yet to be revealed. If convicted, Meadows could face a six-month prison term for each contempt charge, but more likely would be fined.

Accusing the select committee of abusing its powers, Meadows sued its nine members and House Speaker Nancy Pelosi last week, asking a federal court to block enforcement of the subpoenas issued to him and to Verizon for his phone records.

His lawyer George Terwilliger wrote to the panel on Monday to denounce the proposed prosecution as "manifestly unwise, unjust and unfair."

Thousands of Trump supporters, many associated with ultra-nationalist and white supremacist groups, stormed the Capitol 11 months ago in an effort to overturn President Joe Biden's election victory.

In a fiery speech earlier that day, Trump repeated false claims of election fraud that he had been making for months and called on supporters to march on the Capitol and "fight like hell."

The House voted to recommend charges against ex-White House strategist Steve Bannon in October. He faces trial in July on two counts of contempt.

Schiff warned in a statement any other witnesses considering denying subpoenas that they could also face "potential jail time."