The land at Camellia, near Parramatta, was bought for $53.5 million in 2016 to stable and maintain the future Parramatta light rail.

The deal delivered its previous owner - a property developer - a $15 million windfall just seven months after they had bought the site in late 2015.

However, it was far less lucrative for Transport for NSW, with the cost for the six-hectare site's clean-up estimated to reach $100 million.

Transport Minister Andrew Constance last month referred the matter to the state's auditor-general to investigate and also requested the Independent Commission Against Corruption probe the purchase.

The land has since been valued at $15.5 million, and an internal Transport for NSW report handed to the NSW upper house confirms the agency did not obtain a property valuation before paying $53.5 million.

"You don't have to be Einstein to work out something looks very, very fishy there," NSW Labor deputy leader Yasmin Catley told reporters on Monday.

"There was not a valuation report done when that land transaction occurred - that is rotten. This is a complete misuse of public money."

Transport for NSW was outbid for the property in 2015, but decided to compulsorily acquire it in 2016 after confirming its suitability as a tram yard.

The site is contaminated with a range of chemicals including asbestos and hexavalent chromium.

Mr.Constance told reporters on Monday that he was waiting for the auditor-general's findings.

"The community is entitled to open, transparent, accountable actions on behalf of Transport for NSW on behalf of this," Mr Constance said.

The $2.4 billion Parramatta Light Rail, due to open for passengers in late 2023, will connect Westmead to Carlingford via the Parramatta CBD.

Australian Associated Press