The Nationals MP Colin Boyce will challenge David Littleproud for the leadership after declaring the party was “committing political suicide” by ending the Coalition.

The Flynn MP said he would move a motion to spill the Nationals leadership at a party room meeting on Monday, and would stand as a contender.

Nationals MPs immediately dismissed Boyce’s prospects and were confident Littleproud retained the support of most colleagues despite internal unrest over his role in the second Coalition blow-up in eight months.

“I will be moving a spill motion on Monday afternoon in the National party room to give my colleagues an option, because the reality is, if they follow the course they’re on now, we are going over the political cliff,” Boyce told Sky News on Tuesday.

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Confirmation of a Nationals leadership spill comes amid speculation Sussan Ley could also face a challenge when federal parliament returns next week. Ley’s allies continue to doubt that a challenge will eventuate, with conservative contenders Angus Taylor and Andrew Hastie yet to declare their intentions.

Boyce said the Nationals were committing “political suicide” after it quit the Coalition following Ley’s decision to accept the resignations of three senators who crossed the floor to oppose Labor’s hate speech laws.

“The National party now faces a right-flank onslaught from One Nation if they go it alone to the next election,” Boyce said, arguing the Nationals would struggle to fundraise and lose staff numbers and other resources if it continued as a standalone party.

The decision to quit Ley’s frontbench en masse in solidarity with the three senators, effectively ending the Coalition, was made at the National’s party room last Wednesday.

Boyce did not attend that meeting or any others during the chaotic week in Canberra, sources confirmed.

Speculation is rife that Boyce will soon follow former Nationals leader and one-time ally Barnaby Joyce and defect to One Nation.

In the Sky News interview, Boyce denied he was moving to One Nation but said he had seen a surge in support for the rightwing party in his central Queensland seat.

“There is a huge surge up here [for One Nation],” he said.

“There’s lots of people say to me, you know, you should join One Nation and so forth. That’s not happening for me, I am a member of the LNP [Liberal-National party]. I am obligated to do the best I can for the LNP and indeed, the National party in Canberra,” he said.

The former Nationals leader, Michael McCormack, told Guardian Australia he was aware Boyce had been unhappy over the Coalition split but believed Littleproud’s position was “fairly safe”.

McCormack noted the fact that colleagues who were no longer in shadow cabinet positions had lost pay, resources and staff, could throw a “curveball” on Littleproud’s popularity.

“I think David is fairly safe on the numbers,” he said. “I’m disappointed that we are where we are because it could have been so easily avoided … it’s unfortunate that we continue to prosecute these arguments and talk about ourselves instead of the bread and butter issues.”

Another Nationals MP, speaking on the condition of anonymity, agreed Boyce did not have the support of the party room.

However, the MP was unsure if another colleague would stand in addition to Boyce, noting that “nobody” inside the Nationals was happy with the current situation between the Coalition parties, and that there was some anger internally at Littleproud’s actions.

Guardian Australia understands Matt Canavan – who unsuccessfully challenged Littleproud for the leadership after the election – was not expected to put his hand up on Monday.