A key House Freedom Caucus member is predicting that Speaker Kevin McCarthy may not follow through on his word to not bring an omnibus spending bill to the floor at the end of this fiscal year, underscoring the tenuous relationship between House GOP leaders and the hardliners in their conference.

"I've been here eight and a half years, and for eight and a half years, we've done the same thing every time," Rep. Ken Buck, R-Colo., told Fox News Digital in an interview in his office. "Leadership has promised, either Democrat or Republican leadership, has promised that we're going to do 12 appropriations bills. We start on those 12 appropriations bills. There's a hiccup for some reason, the Senate doesn't do that. And we end up doing a large omnibus or, maybe at best, a couple of minute mini-buses."

One of the key promises McCarthy made when he became speaker this year was to not bring an omnibus bill combining all of the government’s spending priorities into a single piece of legislation but rather stick to 12 separate bills.

But Buck instead predicted that Congress would by Sept. 30 settle on a continuing resolution that would extend the current spending priorities for "a matter of six or seven weeks" and then use the holiday season to pressure lawmakers to pass a single large spending bill at the end of the year.

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Ken Buck

Rep. Ken Buck spoke to Fox News Digital about the upcoming appropriations bill during an interview in his office. (Fox News Digital / Liz Elkind)

"You watch, it'll be for Dec. 23. So, that's when the money will run out. And then everybody will say all week, ‘You're going to do this to federal workers, you're going to put them out of work right before Christmas, how heartless. You've got to vote for this ridiculous spending bill,’ so the country is on this terrible path," he said.

Buck was one of several conservatives who tried to stop McCarthy’s debt limit compromise with Biden from coming to the House floor. Last month, he and a similar group of lawmakers halted House floor proceedings for roughly a week in protest over how the debt was handled.

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McCarthy reportedly agreed to keep this year’s appropriations bills to fiscal year 2022 levels, rather than the 2023 levels agreed to in the bipartisan deal, in order to lift the blockade. But Buck said on Tuesday, "The idea that we're going to keep it to 2022 numbers is just not in the cards."

House Minority Leader Kevin McCarthy

Buck said he has "little faith" that GOP leaders like Speaker Kevin McCarthy, above, will follow through on assurances to cut spending. (Drew Angerer / Getty Images / File)

"I don't have a lot of faith that we will reduce spending, we will follow any kind of spending limit. Ultimately, we will end up with a huge spending bill in December," Buck said.

But he would not say what kind of reaction that would elicit from himself and the other GOP rebels.

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"I think there'll be a lot of disappointment in this process," Buck said. "I don't know, you know, one of the things that we don't do is tell people, ‘We're going to shut down the floor.’ Because then other folks can plan on what do they do in the event that that happens. So, if it does happen, it will be spontaneous."

Historically, a failure by Congress to reach a spending deal by Sept. 30 has led to a partial government shutdown. Buck refused to say directly whether he would prefer a shutdown to an omnibus bill, but he did go out of his way to place early blame on Democrats if the situation were to occur.

President Joe Biden

House conservatives retaliated against McCarthy for making a deal with President Biden on the debt limit. (Brendan Smialowski / AFP via Getty Images / File)

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"The real question is: Does government shut down now because we're trying to get our act together and find ways to cut spending or does government shut down in the future because we run out of money?" Buck said. "It's not if government is going to shut down, it's when government's going to shut down. I'm in favor of making sure we reduce the spending as much as possible."

"If the Democrats want to shut down government by refusing to sign on to bills, or the president refuses to sign a bill or the Senate Democrats refuse to pass a responsible bill, that's on the Democrats."