A Nationals senator believes the junior coalition partner still deserves a fourth seat around the cabinet table despite Liberal Ian Macfarlane’s failed bid to switch party camps.

The LNP’s state executive on Monday refused to support the former minister’s attempt to switch to the Nationals partyroom.

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Senator Matt Canavan is disappointed, telling ABC radio on Tuesday the Nationals still deserve another cabinet spot after an “oversight” in a ministerial reshuffle following Malcolm Turnbull’s elevation to Liberal leader.

“I certainly expect that oversight to be rectified,” he said.

Senator Canavan said Mr Macfarlane’s plan to join the Nationals was a way to improve representation of rural Australia, which wasn’t reflected in cabinet.

“Representation in cabinet right now from rural and regional Australia is barely a facade with only three members of the cabinet [living] outside capital cities.”

Nationals deputy leader Barnaby Joyce said allowing Mr Macfarlane to switch camps should have been a formality after the MP received strong support from party members in his Toowoomba-based seat of Groom.

“Why would you vote against Queensland getting better representation?” he told ABC radio of the state executive’s decision.

Mr Joyce said people in regional centres believed the best chance they had of being represented in cabinet was through the Nationals.

He noted the recent replacement of a prime minister from Sydney with another from the NSW capital, along with the two most recent treasurers.