Liz Cheney accused her fellow Republicans of abandoning the rule of law and undermining American democracy on Tuesday night, the eve of a vote in which she is likely to be ousted from the party leadership over her criticisms of Donald Trump.

Speaking on the floor of the US House of Representatives late on Tuesday, Cheney, the Wyoming congresswoman and a daughter of former vice-president Dick Cheney, said the former president posed an unprecedented “threat” to America with his repeated false claims that last year’s election was stolen.

“Our duty is clear. Every one of us who has sworn the oath must act to prevent the unravelling of our democracy,” Cheney said to fellow lawmakers. “Remaining silent, and ignoring the lie, emboldens the liar.“I will not participate in that,” she added. “I will not sit back and watch in silence while others lead our party down a path that abandons the rule of law and joins the former president’s crusade to undermine our democracy.”

Cheney pulled no punches hours ahead of the vote that is likely to see her ousted from her role as House Republican conference chair and the most senior GOP woman on Capitol Hill.

Her dispute with members of her own party has been seen in Washington as a symbol of Trump’s enduring grip on the Republican party.

A staunch conservative, Cheney was seen as a rising star when she was elected to Congress in 2016. But she broke with many of her peers after the January 6 attack on the US Capitol that endangered fellow lawmakers and left five people dead.

Cheney was one of 10 Republican House members to vote to impeach Trump for his role in the riot, which was led by his supporters. She survived a no-confidence vote held by secret ballot in February.

However, her relationship with Kevin McCarthy, the Republican House minority leader, has deteriorated in recent weeks as she continued to publicly criticise the former president.

Trump has called the hawkish congresswoman a “warmonger”, and endorsed New York state’s Elise Stefanik as her replacement for the House role.

McCarthy told colleagues this week that they should “anticipate a vote on recalling the conference chair” on Wednesday.

“Having heard from so many of you in recent days, it’s clear that we need to make a change,” he said in a letter, adding that the Republicans were a “big tent party”.

McCarthy is forming a strategy for the Republicans to take back control of the House in next year’s midterm elections, when the party also hopes to retake control of the Senate.

Critics argue that by ostracising Cheney, the GOP will only further alienate the moderate voters who shunned the party at the ballot box last November.

“Ronald Reagan made it clear that calling our party a big tent was more likely to draw people in, and that is what we needed to win elections,” Mitt Romney, the Utah senator, said on Tuesday. “If you narrow the tent to a pup tent, you make it less likely that we win elections.”

But others have defended the move, saying the GOP should elect leaders who reflect the views of the majority of lawmakers who still support Trump.

Kevin Cramer, the Republican senator from North Dakota, told reporters on Capitol Hill that the party in the Trump era had succeeded in attracting “working-class Americans”.

“We have this great big tent, and there should be room for everybody. But not all of them get to be the leader,” he said of Cheney.

Cheney will remain in Congress following Wednesday’s vote, but she is expected to face several primary challengers in 2022.

“Is being removed from as conference chair a setback? Maybe, but not necessarily,” said Doug Heye, a strategist and former spokesman for the Republican National Committee. “This may free her up to do other things . . . there is definitely a long-term strategy.”