The government has also defended sitting on draft exposure legislation for a national integrity commission since last year, as more details have come to light over the purchase of the land for 10 times more than its value.

The Infrastructure Department official stood down over the affair is being investigated for 21 actions, omissions or failures to act under four main allegations in a code of conduct investigation.

If proven, each of the allegations could represent five or more breaches of the Australian Public Service Code of Conduct, giving rise to a potential of more than 100 breaches of the code.

Finance Secretary Rosemary Huxtable told Senate estimates on Wednesday that even though her department holds the government purse-strings, her department wasn't consulted on the valuation strategy, which is at the crux of the inflated payment for the land.

"We were not consulted on this valuation strategy, and in my reading of the [ANAO] report, is that it's this valuation strategy which created an environment in which a valuation of $29.8 million was concluded," Ms Huxtable said.

The audit report into the purchase made no findings about the Department of Finance, and Ms Huxtable said her department was involved in the acquisition strategy, but the two strategies were different.

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While questions continued about the land, Prime Minister Scott Morrison said public servants shouldn't be diverted from dealing with the bushfires and COVID-19 pandemic to progress legislation for a national anti-corruption body.

A Senate committee heard the draft legislation was handed to Attorney-General Christian Porter in December, but Mr Porter said the government had chosen not to start a consultation process in the middle of the pandemic.

"The next stage for the integrity commission will be a consultation phase. That will be detailed and it will be extensive," he said.

The Greens have jumped on evidence from officials in his department that a reference to 76 staff for the integrity commission in the budget papers for this year was included "in error" and should have been edited out.

"I think it was an oversight from previous budget measures that shouldn't have been included in that paper and would ordinarily have been edited, but that was missed," deputy secretary Sarah Chidgey said.

Issues around potential corruption have dominated political debate, as the letter to the suspended public servant reveals a series of alleged actions and failures, that will be investigated by former inspector general of intelligence and security Vivienne Thom.

The allegations include procuring a land valuer suggested by the owner of the Leppington Triangle land, failing to maintain appropriate records, failing to properly brief senior officials and ministers, and conducting a meeting with a landholder in a coffee shop with no other employees present, and no records kept.

Conduct around the purchase of the land is also being investigated by the Australian Federal Police, after Auditor-General Grant Hehir said the series of unexplained actions related to the payment was "suggestive of the fact that the Commonwealth may have been defrauded".

"Somebody in Infrastructure did something wrong, so much has been established," Finance Minister Mathias Cormann said on Wednesday.