WASHINGTON — Lawmakers investigating the deadly assault on the US Capitol said Thursday they were pursuing criminal contempt charges for a key ally of former president Donald Trump for refusing to testify.

Former White House advisor Steve Bannon had already made clear he had no intention of complying with a subpoena to appear Thursday before the cross-party January 6 congressional select committee.

The right wing strategist told the panel he would withhold testimony and documents until Trump’s claim of “executive privilege,” which allows presidents to keep certain conversations with aides secret, had been resolved.

“We reject his position entirely,” committee chairman Bennie Thompson said in a statement.

“The select committee will not tolerate defiance of our subpoenas, so we must move forward with proceedings to refer Mr Bannon for criminal contempt.”

The panel — which is unified in its aim to enforce subpoenas — will meet on Tuesday next week to vote on adopting a contempt report setting out the case against Bannon, Thompson said.

The Democratic-controlled House of Representatives would then vote to refer Bannon to the Justice Department to consider charges.

A timetable for that decision has yet to be revealed. If convicted, Bannon would face up to 12 months in prison, but more likely a fine.

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

They had been egged on by Trump, whose fiery speech earlier that day falsely claiming election fraud was the culmination of months of baseless claims about a contest he lost fairly to Biden.

A comfortable majority of 57 senators — including seven from his own party — voted to convict Trump after he was impeached by the House for inciting the riot, although this fell short of the two-thirds majority required under Senate rules to unseat a president.

Bannon himself was charged in August last year with conspiracy to commit wire fraud and money laundering after allegedly defrauding thousands of donors to a campaign to help build Trump’s wall along the southern border.

Trump pardoned Bannon in the final hours of the former president’s White House term.

Trump opponents saw the move as a “thank you” from the ex-president after Bannon refused to cooperate with the House’s investigation into Russian interference in the 2016 election.

“He felt he could do that because he would never be held in contempt, he would never be prosecuted, by the Trump justice department,” January 6 committee member Adam Schiff told MSNBC on Wednesday.

“But those days are over. It is essential to our investigation. But I also view this, the enforcement of the rule of law, as an early test of whether our democracy is recovering.”