A federal appeals court has upheld the criminal conviction of former Trump strategist Steve Bannon.
The decision may soon send Bannon, 70, to prison, after years of legal wrangling.
He was convicted in 2022 of contempt of Congress for refusing to provide testimony or documents to the committee probing the 6 January Capitol riot.
Bannon's lawyer said he would file new appeal, adding there were "important constitutional issues at stake" .
Bannon was sentenced to four months in prison and ordered to pay a fine of $6,500 (£5,200).
But the right-wing podcaster, who has denied any criminal wrongdoing, was able to remain out of jail on bond while challenging his conviction.
Bannon's lawyers have characterised the case as politically motivated and said that he was attempting to negotiate - rather than ignore - the committee's subpoenas.
Bannon himself has maintained that he was following legal advice when he refused to testify before the House committee investigating the 2021 attack that was intended to stop Congress from certifying Joe Biden won the 2020 election.
In a unanimous decision, the US DC Circuit Court of Appeals rejected Bannon's argument, saying it "runs headlong into settled law".
"This exact 'advice of counsel' defense is no defense at all," wrote Justice Bradley Garcia, a Biden appointee, on behalf of the court, a panel that also included a Trump appointee and an Obama appointee.
Bannon was not ordered to immediately begin his four-month term. He now has seven days to file another appeal.
David Schoen, his lawyer, said that he would ask the full 11-member DC appeals court to hear the case.
Mr Schoen argued that Donald Trump had invoked executive privilege - a legal concept which allows presidents to keep some communications private - and that Bannon would be breaking the law if he testified in front of Congress.
Bannon's legal team advised him, Mr Schoen said, "in no uncertain terms that he was not permitted as a matter of law to in any way respond to the subpoena".
Peter Navarro, another senior Trump aide, reported to prison in March after his own contempt of Congress conviction.
In a 2021 memoir - In Trump Time - Navarro said he was the architect of a strategy to challenge the 2020 election's results that made Joe Biden president.
Bannon was a key player in Mr Trump's successful 2016 election campaign and later took the role of chief strategist at the White House.
He left that position following a violent far-right rally in Charlottesville, Virginia, in August 2017. Even after his departure, the combative podcaster was considered a top ally of Mr Trump.
