Labor is demanding more answers after an audit found the federal government spent 10 times the market value on land for the Western Sydney Airport development.

The National Audit Office found the government paid almost $30 million for the 12-hectare plot when it was only worth $3 million.

The price was 22 times higher per hectare than what the NSW government paid for its portion.

The audit office found the federal infrastructure department did not exercise appropriate due diligence and fell short of ethical standards.

Labor’s Catherine King said the deputy prime minister and urban infrastructure minister must explain the findings, describing the purchase as a comprehensive waste of taxpayer money.

“If Australians cannot trust the Morrison government with this infrastructure spend, it will be impossible to trust them with future investments,” she said on Tuesday.