Ministerial diary notes reveal Ms Trad and ministerial staff met with the Plenary Group on September 1, during this year's Labor state conference.

Plenary Group is part of a consortium which has been short-listed for the Cross River Rail's tunnel, stations and development contract.

During question time in Parliament, LNP leader Deb Frecklington accused Ms Trad of breaching probity rules, and said the meeting appeared to be held without a probity officer being present.

"Why did the Treasurer hold an $11,000 cash-for-access meeting with a company at the same time the Treasurer is actively considering that company to be awarded billions of dollars of government contracts?" Ms Frecklington asked.

Ms Trad said Ms Frecklington's categorisation of the event was "absolutely incorrect".

"There was no discussion with anyone in relation to the Cross River Rail project," she said.

"I ensured that there was a staff member present and notes were taken of that meeting."

Ms Trad said she had complied with Cross River Rail probity processes at all times.

She tabled protocols, which stated state meetings should not be held with bidding organisations to discuss issues relating to the Cross River Rail project without notifying the Cross River Rail Delivery Authority chief executive.

If an interaction did occur, for example while attending an event, with any of the bidders, Ms Trad would be prevented from specifically discussing the project.

Ms Trad said the meeting with the Plenary Group was transparently published in her ministerial diary.

"That meeting was largely social in nature and there were no issues of substance discussed that required formal notes or any follow-up action," she said.

"The Cross River Rail project was not discussed at this meeting in accordance with the probity protocols."

Ms Trad said the successful consortium would be chosen based on the strength of their offer in meeting the state's requirement for Cross River Rail.

"The Cross River Rail Delivery Authority which is an independent authority ... is doing the assessment of all of the bids," she said.

The Cross River Rail Delivery Authority will make its recommendation on the bids to the government to sign-off in the first half of 2019.

A Plenary Group spokeswoman said the company attended policy forums and other events on both sides of politics where policy and infrastructure issues were discussed.

"Our focus is to gain a current understanding of infrastructure policy direction," she said.

"We do not discuss procurement processes."

Ms Frecklington also questioned whether Ms Trad sought advice from the probity officer before talking about Cross River Rail during a lunch in New York in September hosted by the Queensland Investment Corporation, which was also a shortlisted bidder.

An official travel report says matters discussed included: "The $45.8 billion capital program over the next four years that will drive jobs and economic opportunities with major [projects] such as Cross River Rail."

Ms Trad said the post-budget Queensland Treasury Corporation and QIC roadshow had been held every year since Sir Leo Hielscher was the under treasurer.

"QIC has been a part of this program for many years and they were a part of this program this time," she said.

"I have made it clear to absolutely every single participant in the consortiums, in the alliance, that there will be no discussion by me or any member of my staff in relation to this project and their bids."

Ms Frecklington said the LNP had written to the probity auditor about its concerns.

"[This] could expose the government to legal action from unsuccessful bidders," she said.

"That will only cost the taxpayers of Queensland hundreds of thousands, if not millions of dollars and that is distressing.

"The Treasurer has some serious questions of integrity, accountability and trust to answer."

Ms Frecklington said Ms Trad should have kept notes of the Plenary meeting, discussed it with the probity officer or had the probity officer in the room.