WASHINGTON — The House voted on Thursday to find Stephen K. Bannon in criminal contempt of Congress for stonewalling the investigation into the Jan. 6 Capitol attack, taking action against a close ally of former President Donald J. Trump as he and Republicans veered deeper into their efforts to justify the violence with false claims of a stolen election.

The vote of 229 to 202, mostly along party lines, came after Mr. Bannon refused to comply with a subpoena from the House select committee investigating the riot, declining to provide the panel with documents and testimony. The action sent the matter to the Justice Department, which now must decide whether to prosecute Mr. Bannon and potentially set off a prolonged legal fight.

But what was clear on Thursday in the debate before the vote was that nine months after the deadliest attack on the Capitol in two centuries, most Republicans remained bent on whitewashing, ignoring or even validating the mob violence on Jan. 6 in Mr. Trump’s name, based on his lie of election fraud.

They did so seemingly at the direction of Mr. Trump himself, who in a statement before the vote derided the election he lost as a crime and praised the mob attack — which injured 140 police officers and claimed several lives — as a legitimate response.

“The insurrection took place on Nov. 3, Election Day,” Mr. Trump wrote. “Jan. 6 was the protest!”

On the floor of the House, Representative Jim McGovern, Democrat of Massachusetts, condemned the former president’s comments.

“We live in an age where apparently some put fidelity to Donald Trump over fidelity to the Constitution. I find that disgusting,” Mr. McGovern said.

“He is so feared,” Mr. McGovern added, “that my Republican colleagues are going to keep denying what happened that day.”

The question of what will happen to Mr. Bannon will now go to the Justice Department, where Attorney General Merrick B. Garland has declined to say whether he will move forward with charges.

“We’ll apply the facts in the law and make a decision, consistent with the principles of prosecution,” he told the House Judiciary Committee during an oversight hearing on Thursday.

President Biden has endorsed prosecuting those who do not cooperate with the investigation. On Thursday, he made a point of condemning the riot and its origins.

“The violent, deadly insurrection on the Capitol nine months ago — it was about white supremacy,” Mr. Biden said in a speech on Thursday to commemorate the 10th anniversary of the Martin Luther King Jr. monument in Washington.

Robert J. Costello, Mr. Bannon’s lawyer, informed the House committee that his client would not comply with its subpoena, citing Mr. Trump’s directive for his former aides and advisers to invoke immunity and refrain from turning over documents that might be protected under executive privilege.

Under federal law, any person summoned as a congressional witness who refuses to comply can face a misdemeanor charge that carries a fine of $100 to $100,000 and a jail sentence of one month to one year.

Members of the investigative committee, which is controlled by Democrats, believe that Mr. Bannon has crucial information about plans to undermine Mr. Biden’s victory, including conversations Mr. Bannon had with Mr. Trump in which he urged the former president to focus his efforts on Jan. 6.

In a report recommending that the House find Mr. Bannon in contempt, the committee repeatedly cited comments he made on his radio show on Jan. 5 — when Mr. Bannon promised “all hell is going to break loose tomorrow” — as evidence that “he had some foreknowledge about extreme events that would occur the next day.”

Representative Liz Cheney, Republican of Wyoming and the committee’s vice chairwoman, has suggested that Mr. Trump’s insistence on executive privilege is evidence he was closely involved in the plot to overturn the election on Jan. 6.

“Mr. Bannon’s and Mr. Trump’s privilege arguments do appear to reveal one thing, however: They suggest that President Trump was personally involved in the planning and execution of Jan. 6,” Ms. Cheney said.

She was one of nine Republicans to join House Democrats in voting to find Mr. Bannon in criminal contempt. The others were Representatives Adam Kinzinger of Illinois, the other Republican member of the panel; Anthony Gonzalez of Ohio; John Katko of New York; Nancy Mace of South Carolina; Jaime Herrera Beutler of Washington; Brian Fitzpatrick of Pennsylvania; and Fred Upton and Peter Meijer, both of Michigan.

Representative Kevin McCarthy of California had encouraged fellow Republicans to oppose the contempt referral. He called the committee’s subpoena “invalid” and said he agreed with Mr. Bannon that a court should decide whether the former Trump adviser should comply.

“They are using this to target their opponents,” Mr. McCarthy said.