The US House of Representatives has voted to create an independent commission on the deadly January 6 insurrection at the Capitol

The House’s approval sends the legislation to an uncertain future in the Senate, as Republican increasingly line up against the bipartisan investigation and align themselves with former President Donald Trump.

Democrats say an independent investigation is crucial to achieve a reckoning on what happened that day, when a violent mob of Trump supporters smashed into the Capitol to try to overturn Joe Biden’s election victory.

Modelled on the investigation into the 9-11 attacks of 2001, the legislation would establish an independent, 10-member commission that would make recommendations by the end of the year for securing the Capitol and preventing another insurrection. It passed the House 252-175.

But top Republicans in Congress are working to stop it. Senate Republican leader Mitch McConnell said he would oppose the legislation, joining with House GOP leader Kevin McCarthy, who came out against it on Tuesday. Both men claimed the bill was partisan, even though membership of the proposed commission would be evenly split between the parties.

The January insurrection has become an increasingly fraught topic for Republicans, with a growing number in the party downplaying the severity of the worst attack on the Capitol in more than 200 years.

While most Republicans voted against forming the commission, only a few spoke on the floor against it. And a handful of Republicans who backed the commission spoke forcefully.

“This is about facts — it’s not partisan politics,” said New York Representative John Katko, the top Republican on the House Homeland Security Committee who negotiated the legislation with Democrats.

He said “the American people and the Capitol Police deserve answers, and action as soon as possible to ensure that nothing like this ever happens again”.

Republican Representative Fred Upton said January 6 would “haunt this institution for a long, long time” and that a commission was necessary to find the truth about what happened. He recalled that he “heard the shouts, saw the flash-bangs, smelled the gas on that sorry day”.

Democrats grew angry as some Republicans suggested the commission was only intended to smear Mr Trump.

Several shared their own memories of the insurrection, when rioters brutally beat police, broke in through windows and doors and sent politicians running.

Four of the rioters died, including a woman who was shot and killed by police as she tried to break into the House chamber. A Capitol Police officer collapsed and died after engaging with the protesters, and two officers took their own lives in the days after.

“We have people scaling the Capitol, hitting the Capitol Police with lead pipes across the head, and we can’t get bipartisanship? What else has to happen in this country?” Democratic Representative Tim Ryan shouted on the floor just before the vote. He said the GOP opposition was “a slap in the face to every rank and file cop in the United States”.

The vote was yet another test of Republican loyalty to Mr Trump, whose grip on the party remains strong despite his election defeat.

House Republicans removed Wyoming Representative Liz Cheney from their leadership last week for her criticism of Mr Trump’s false claims, installing a Trump loyalist in her place.

Ms Cheney, in turn, suggested to ABC News that a commission could subpoena Mr McCarthy because he spoke to Mr Trump during the insurrection.

Democratic House Speaker Nancy Pelosi called Mr McCarthy’s opposition to the commission “cowardice”.