Queensland MP Ian Macfarlane’s decision to leave the Liberal Party for the Nationals is “disappointing”, government frontbencher Christopher Pyne says.

Mr Macfarlane was industry and science minister under former Prime Minister Tony Abbott but was dropped from the coalition’s ministry line-up when Malcolm Turnbull took over.

Other Liberal MPs have also criticised Mr Macfarlane’s shift to the Nationals, as talks are set on on a possible new ministry role for the coalition government partner.

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“I’m sorry he was disappointed he was asked to retire from the cabinet but he has been in the cabinet since 2000 so he has had a pretty good run in the cabinet,” Mr Pyne told the Nine Network on Friday.

“I was disappointed,” he said of Mr Macfarlane’s decision.

Malcolm Turnbull is set to meet with National Leader Warren Truss within weeks to discuss an extra ministry position for the Nationals.

Mr Pyne said he was disappointed in the decision. Photo: AAP

The switch has been met with outrage from some Liberals who have accused Mr Macfarlane of blatant self-interest.

The move – if approved by Mr Macfarlane’s Groom electorate council on December 12 – will take the Nationals’ numbers to 22, which members said changed the ratio determining how many ministries were given to the junior coalition partner.

Mr Macfarlane first began talking to Mr Truss about the idea when he was dumped from the ministry by Mr Turnbull after the ousting of Tony Abbott in September.

Senior Nationals sources said media reports of Deputy Leader Barnaby Joyce’s involvement in the switch were incorrect and he had no knowledge of the move until about a fortnight ago.

Victorian Liberal MP Dan Tehan said it was done for “naked ambition”.

“What we shouldn’t be seeing is people trying to game the system for their own self-advancement,” Mr Tehan told ABC radio.

Nationals Senator John Williams said there was a clear agreement “the more seats you hold the more rights you have” to ministry positions.

Northern Territory Country Liberal Party MP Natasha Griggs said she was also approached to switch but declined.

Opposition Leader Bill Shorten said on Friday that it was the first visible crack in the Turnbull government.

“It seems to me that Malcolm Turnbull’s judgment is definitely under scrutiny because we’ve got the crazy situation where he promoted the wrong man, Mal Brough, and demoted the right guy, Ian Macfarlane,” Mr Shorten said.

Nationals frontbencher Darren Chester, who was in Groom on Friday with Mr Macfarlane, said his colleague had no expectations of being guaranteed any senior role in the future.

“Nothing was offered to Mr Macfarlane by the National party for him to change the party he wanted to sit with in Canberra,” Mr Chester told Sky News.

Mr Chester said Mr Truss had the support of his party members until he decided to leave the job.

After that, it was reasonable to expect that part of an orderly succession Mr Joyce would step up from deputy to be leader, Mr Chester said.

A Nationals source told AAP Mr Joyce should not assume he will get the leadership, given some of his failings as a minister.