A $600 million AusNet Services contract signed by Downer EDI in 2019 has been named in legal filings as being the heart of the “accounting irregularity” that wiped more than half a billion dollars off the company’s market capitalisation last year.

Downer stunned investors in early December when it revealed that it would have to restate profits by tens of millions of dollars due to the misreporting of revenues and work-in-progress on a maintenance contract for a power customer, causing its share price to tumble 20 per cent in one day.