Mr Powderly has written to the ACT committee investigating the affair, saying Colliers had never been asked to provide a formal valuation on the land in Glebe Park that the government bought from businessmen Graham Potts, Barry Morris, Richard Tindale and Joe Bisa for $3.8 million (plus GST) in 2015.

Auditor-General Maxine Cooper found the purchase, and two others at the lake, lacked transparency, accountability and rigour. She criticised the lack of a formal valuation for the Glebe Park block, with the land agency instead relying on informal advice from Colliers for the price. She also questioned why Colliers had arranged the negotiation meeting between the government and the Glebe Park owners, and highlighted a document that was "manipulated" before being released after a freedom of information request.

The document was a "discussion paper" on the value of Glebe Park, the title of which was changed to "valuation advice" before it was released.

Dr Cooper said after receiving the freedom of information request, the land agency could not find a copy of the advice, so had asked Colliers to re-send it. The Colliers principal (Mr Powderly) had sent a copy of the "Discussion Paper" on November 12 2015 at 9.57, offering "If you want it changed to say valuation advice I can change."

Eight minutes later, he sent a new email attaching the advice again, this time with the title "Valuation Advice".

But Mr Powderly has told the parliamentary inquiry that the request to change the title came from a former employee of the Land Development Agency.

"After receiving, he called back and asked if I could change the title of the discussion paper to say "valuation considerations" or "valuation advice". It was not a formal valuation so I was happy to assist given this is was [sic] the title was in the first paper."

The former employee had "got into trouble" for asking for the change, Mr Powderly said in a letter to the inquiry.

In evidence to the inquiry in September, Mr Powderly said he had been out of the office at the time, but his assistant had sent the discussion paper to "John", a person he identified under questioning as former acting sales, marketing and land management director John Mason.

While the auditor said the changed document had been sent only eight minutes after the "discussion paper", Mr Powderly told the inquiry he had received a call from the agency about 30 or 40 minutes after sending the discussion paper, when the agency had asked him to change the title.

He said he had told the agency, 'I have no issue with it … but I don't understand why you'd want to have a discussion paper labelled that."

The discussion paper was the second of two pieces of valuation advice provided by Mr Powderly in May 2015. The first was titled "Valuation Considerations" and handed to former land agency deputy chief executive Dan Stewart on June 16. The "Discussion Paper" was sent a week later.

Dr Cooper has pointed out that while the first paper says the zone does not allow residential use, the second, the one whose title was changed, said the zone allows residential.

Both recommended $3.6 million to $3.8 million.

Mr Powderly referred to an article published in the Canberra Times in June 2015, which he said contained "incorrect information concerning the advice Colliers International had provided." He does not specify but is presumably referring to stories that quoted former land agency head David Dawes saying Colliers had provided a valuation.

Mr Powderly said he had never provided a formal valuation to the agency and had never been asked to.

"Colliers International has received unfair criticism for assisting the LDA with this intital advice, which was not formal valuation advice and nor did we receive any payment," he wrote.

He had told Dan Stewart that if the deal went ahead the agency should get a formal valuation, he said.

Mr Powderly has released a file note from June 19 2015, the day the deal was done, in which he writes, "If Dan buys can provide valuation advice to replace paper."

As to why he set up the negotiation meeting between Mr Stewart and the block owners, Mr Powderly told the inquiry he had offered to organise it "as I knew the owners". Colliers sells properties for Mr Morris's Morris Property and Mr Potts's Amalgamated Property.

Mr Powderly told the inquiry in September that the agency's failure to get formal valuation advice "has meant that my papers have ended up being gospel and viable and everyone holding them to be something greater than they are".

Mr Powderly appears before the inquiry again on Wednesday, as does ACT solicitor-general Peter Garrisson.