West Australian Greens Senator Scott Ludlam says he has no confidence the state's laws can protect the environment following the handling of the contentious Perth Freight Link project.

The Office of the Environmental Protection Authority’s audit of the site was released on Wednesday, which found there was only one breach of environmental conditions despite a Senate committee inquiry previously shown multiple acts of non-compliance.

Independent auditors visited the Beeliar Wetlands site daily from December 6 to February 10 and found there was no signage of mulch stockpiles, but otherwise assessed that Main Roads WA and the construction contractors displayed a “high level of commitment and performance”.

Senator Ludlam said the audit findings were “appalling but not surprising”, and the environmental authority had been sent 150 pages of evidence from community groups showing the conditions had been breached.

“I’ve stood at that fence line and seen trucks obliterating vegetation,” he said on Wednesday.

“I know for a fact there’s been breaches. I’ve seen them with my own eyes.”

All work was suspended at the Beeliar Wetlands after Labor won the March state election, as stopping the project was one of the party’s key campaign promises.

The Senate committee inquiry, initiated by Senator Ludlam, recommended ahead of the election that work be immediately halted, after being shown evidence of contractors breaching environmental conditions, particularly surveys of vulnerable black cockatoo nesting trees.

Senator Ludlam said the project showed WA’s environmental laws were “hollow”, as legal challenges to the highway extension outlined that the EPA’s own environmental policies were not legally binding on them, but were merely guidelines.

An Office of the Environmental Protection Authority spokeswoman suggested evidence used for the audit was not presented to the Senate committee inquiry due to timing and that aside from mulch signage, all requirements were met.

“As the state government was in a caretaker period when the Senate inquiry was held, and given the issue had become a focal point for the election, it was inappropriate for state government employees to attend a federal inquiry into the alleged environmental breaches,” she said.

Senator Ludlam said there had been no rules prohibiting them from fronting the inquiry.

By Rebecca Gredley