Democrats need to “get up off our rear ends” and work to bring down prices and runaway inflation, or face wipeout in November’s midterm elections, the Massachusetts senator Elizabeth Warren warns.

In a forthright interview Sunday morning on CNN’s State of the Union, the former candidate for her party’s presidential nomination also lambasted the Republican House minority leader Kevin McCarthy as “a liar and a traitor” after he was caught on tape lying about his support for Donald Trump after the 6 January insurrection.

McCarthy could become House speaker if Republicans, as polls suggest, win back control of Congress later this year, something Warren said is a worrying possibility.

“I think we’re gonna be in real trouble if we don’t get up and deliver,” she said.

“I am glad to talk about what we’ve done, obviously, and I think the president deserves real credit, but it’s not enough. We’ve got less than 200 days until the election and American families are hurting. Our job, while we are here in the majority, is to deliver on behalf of those families.”

Warren was echoing growing concerns in Democratic circles that, despite Joe Biden’s bipartisan achievements such as the $1.9tn infrastructure bill, the party is losing out in messaging to Republican culture wars over abortion, transgender rights and race.

“We can’t just rest on what we’ve already done,” she said. “We need to be fighting going forward. There are things that the American people elected us to do and we still need to get out there and do them.”

She added: “We do that then we’re going to be fine in the election. That’s how democracy works, especially when we’re up against a party that just wants to fight culture wars. That’s not gonna help people in their lives.

“Our job as Democrats is to help hard working Americans, and we can do that. We can make government work not just for the billionaires, not just for the giant corporations. We can actually make it work for everyone but we need to get up and do it.”

Warren said she sees inflation, which this month reached a 40-year high, among the biggest obstacles to Democrats’ prospects in midterms.

“Families are paying more at the pump, they’re paying more when they go to the grocery store, they’re paying more when they try to buy a hamburger,” Warren said. “So it’s the responsibility of Congress, of the president, to get out there and make the changes we need to make to bring down those prices for families.

“We can do that. We have the tools, but we’ve got to get up off our rear ends and make it happen. Take it to the people what we’ve [already] done, but we need to get the work done.”

Warren also delivered probably the most caustic comments yet from a senior Democrat over the McCarthy tapes, which the New York Times published last week. McCarthy, who had strongly denied that he ever said he would seek Trump’s resignation for inciting the 6 January Capitol attack, was caught on video saying just that.

“Kevin McCarthy is a liar and a traitor,” Warren said.

“This is outrageous. And that is really the illness that pervades the Republican leadership right now, that they say one thing to the American public and something else in private.

“What happened was an attempt to overthrow our government and the Republicans instead want to continue to try to figure out how to make the 2020 election [result] different. Shame on Kevin McCarthy.”

In a later appearance on NBC’s Meet the Press, Warren, a former frontrunner who dropped out of the 2020 race eight months before election day, ruled out another challenge for the presidency in two years’ time.

“I’m not running for president in 2024. I’m running for Senate. President Biden is running for re-election in 2024, and I’m supporting him,” she said.

Meanwhile, the Republican Missouri senator Roy Blunt, said he was “surprised” by the McCarthy tapes, and that he expected it would be a challenge for the minority leader to become House speaker if his party regains the majority in the midterms.

“Anybody who’s been as close to President Trump, as Kevin McCarthy was, would know that the last thing Donald Trump was going to do was either resign or quit,” he told Meet the Press.

“It was 10 days to the end of his term, and there was no way that was going to happen, and I was frankly so surprised that Kevin would even suggest it might be a realistic suggestion to make.

“When you want to be speaker you don’t just get the majority of your members, you have to get almost all of your members, and that’s challenging. But I think a lot of things will happen between now and November.”