Angus Taylor did not declare at a meeting with environmental officials on endangered grasslands that he had a financial interest in a company under investigation for poisoning.
And no note was taken from the senior department official who attended the meeting in 2017, he heard a Senate committee.
The officials of the Department of Environment and Energy provided evidence during a special hearing of the Senate investigation into the extinction crisis on Friday.
The audition focused on the prairies and, in particular, a March 2017 meeting between Taylor, senior officials and the office of the then Environment Minister Josh Frydenberg to discuss the designation by of the federal government of endangered grasslands known as the temperate natural grasslands of the south-east Highlands.
At the time of the meeting, New South Wales and federal investigations were underway on the poisoning of some 30 hectares that contained the herbs on a property in the Monaro region of the state owned by Jam Land Pty Ltd.
One of the directors of that company is Richard Taylor, the minister's brother, and the minister himself holds an interest in the company through his family investment company, Gufee.
At the hearing on Friday, the department's compliance officer, Monica Collins, told the senators that she was aware before the March 2017 meeting of Angus Taylor's family connection with Richard Taylor.
But he acknowledged that the compliance team investigating the case was also aware of the minister's financial interest in Jam Land.
"We were aware that Angus Taylor was the brother of one of the land managers we were investigating," he said.
Collins also confirmed that investigations into Jam Land were the only case of compliance regarding these grasslands.
Geoff Richardson, assistant branch secretary of the department and protected communities of the department, was one of the officials of the March 2017 meeting.
He told the hearing that Taylor had not disclosed his commercial interest at the beginning of the meeting.
"Has Minister Taylor declared in view of meeting his business interests in Jam Land?" Asked the Labor senator Katy Gallagher.
"No senator, no interest was revealed at the beginning of the meeting, but the meeting was about the list of lawns," Richardson replied.
"Don't you think it was relevant?" Gallagher asked.
"I don't have a vision, Senator," Richardson said.
Greens senator Janet Rice, chairman of the commission, asked again: "And did minister Taylor not declare his personal interest?"
"No senator," replied Richardson.
Taylor and the government have repeatedly stated that the meeting did not discuss the compliance action involving the Taylor company and focused on the prairies listing process.
Taylor said the issue was troubling for his constituents at Hume's electorate.
On Friday, department officials reiterated that the compliance action was not discussed at the meeting. Richardson said that "it was not raised, it was not discussed".
When Gallagher asked if Richardson had taken notes during the meeting, he said no.
At the start of the day, former National Senator John Williams said he had also raised the issue of grasslands with Frydenberg after listening to Richard Taylor on the radio at the end of 2017.
The committee felt that there was a meeting with members of the national party, Frydenberg and the deputy secretary of the environmental protection group Dean Knudson in October 2017 on the issue and concerns. more extensive relating to environmental laws and agriculture.
Knudson said he didn't even have notes from that meeting.
"Now we have been told two fairly critical meetings about this whole problem that the department has not kept track of," Gallagher said.