Barnaby Joyce says he has "absolutely nothing to hide" over a controversial $80 million water purchase made when he was water minister.
"This is an absolute load of horse poo because we did nothing but our job," the former deputy prime minister told ABC Radio on Monday.
The Greens are calling for a royal commission into the Murray-Darling Basin Plan over the water buyback from two properties in 2017, and Labor has left the door open to supporting their push.
Labor has demanded more information on the purchase from the Agriculture and Water Resources Department, with party water spokesman Tony Burke believing it was over the odds.
"You don't pay Versace prices for water that you get from The Reject Shop and that looks like what Barnaby Joyce has done," he told reporters in Cairns.
Prime Minister Scott Morrison on Monday defended the buyback, saying the company's original asking price had been more than $5000 a megalitre, much higher than the agreed price of about $2700 a megalitre.
In August 2017, the government bought 28.7 gigalitres of water from two Eastern Australia Agriculture-owned properties, Clyde and Kia Ora, in Queensland at a cost of $78.9 million.
Mr Morrison said the previous Labor government also bought water off the company, including a $300 million purchase.
Labor says the difference is its buybacks were conducted through a competitive tender process.
The prime minister also defended Mr Joyce and Energy Minister Angus Taylor.
Mr Taylor co-founded the company that sold the water, but has said he had nothing to do with it since entering parliament and received no benefit from the sale.
"The information that's been made available to the Senate inquiry directly by the department makes it very clear that these arrangements were conducted at complete arm's length from any ministers," Mr Morrison told reporters in Melbourne.
Mr Joyce later backed up the sentiment that he was at arm's length from the purchase.
He stressed that he was following a precedent set by Labor and that it was not his job to inquire as to the headquarters of the company.
Eastern Australia Agriculture's parent company is based in the Cayman Islands, a well-known tax haven.
"It is not the question of the minister to decide what the tax consequences are of the person who purchases it, it's not in your remit," Mr Joyce said.
Mr Joyce said he would not be concerned if documents from a Senate inquiry that covered the matter that were redacted were released in full.
"I don't care if they are. I have absolutely nothing to hide."
Australian Associated Press