Up to 25 projects worth billions of dollars in Western Australia could be at risk due to a “technical error” in their environmental approval.
The projects, mainly large mining ventures, were approved between 2002 to 2012 by several Environmental Protection Agency (EPA) board members who had a conflict of interest.
The WA government will introduce legislation on Wednesday to validate the projects' environmental approval.
But environment minister Albert Jacob admitted there was potential for significant market uncertainty until the assessments were validated.
Mr Jacob, who refused to name the 25 projects before tabling them in parliament, said he was incredibly disappointed the mistake had happened but was working to fix the problem.
The EPA's oversight was revealed following the WA Supreme Court's decision in August last year to rule the environmental approval process for the Woodside-led Browse gas project unlawful.
EPA chairman Paul Vogel said he refused to fall on his sword over the regrettable error of judgment and no one had intended to corrupt the process.
Mr Vogel said the environment was not at risk and the EPA's governance procedure had undergone a complete health check to ensure it met legislative requirements.
"In no way do these conflicts (alter) the science of evidence that sits behind every environmental assessment process that we conduct," Mr Vogel said.
"My judgment at the time was based on Section 13. That was found to be flawed - I accept that.
"I genuinely believed at the time I was managing those conflicts appropriately."
The legislation will not validate the Browse proposal, which is currently being reassessed by an independent panel, Mr Jacob said.