Queensland Opposition Leader Deb Frecklington will recommend former treasurer Curtis Pitt be referred to the parliament's Ethics Committee over claims he misled the chamber and voters.
Mr Pitt has strongly rejected the claims.
Ms Frecklington says the LNP has documents showing Mr Pitt signed a draft direction instructing the Queensland Rail board to accept a new enterprise agreement with the unions in late 2016, a claim he has rejected.
But months later, in February 2017, Mr Pitt told the parliament he had not issued a direction to QR.
However, he did say both he and then-transport minister Stirling Hinchliffe had "put very clearly our views of what should be happening in this space on the record and to the board for their consideration."
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Ms Frecklington said Mr Pitt also claimed the QR board had recommended the agreement be signed when the documents showed otherwise.
"The CEO of QR had written suggesting there were major problems there," she said on Friday.
Ms Frecklington said Mr Pitt had a "clear case to answer".
"Queenslanders ask one thing from their politicians and that is honesty," she said.
"After looking at these documents it is clear that Curtis Pitt has failed that test of honesty."
She said she would be writing to outgoing Speaker Peter Wellington to recommend he refer Mr Pitt to the parliament's Ethics Committee.
But she would not be drawn on whether the government should still put forward Mr Pitt as the next speaker when parliament resumes next month.
"That's up to (Premier) Annastacia Palaszczuk to determine whether she thinks Mr Pitt is above reproach and should hold that position," she said.
Mr Pitt denied misleading parliament.
"I categorically refute any suggestion that I have misled parliament and I would be more than happy to provide the Speaker with any further information or clarification should he request it," he said.
Responding to Ms Frecklington's recommendation, a spokesman for Ms Palaszczuk said enterprise agreements for QR staff were approved by its board.
"Enterprise Agreements were considered as part of the comprehensive Strachan Inquiry and its detailed recommendations are being implemented," he said.
"The LNP has no genuine interest in resolving the train crewing issues at Queensland Rail that they helped created by sacking QR staff, including trainer drivers.
"Ms Frecklington has no regard for the Ethics Committee.
"She promoted the two LNP members, Ann Leahy and Stephen Bennett, who had adverse findings from the Ethics Committee, to shadow ministry positions."
