South Australia's opposition says the state government's denials that a harmful algal bloom was toxic have been proven wrong following a revealing report.
It is a year since the first public reports in SA of a mystery foam at a Fleurieu Peninsula beach which made surfers ill and caused dead fish to wash ashore.
The karenia algal bloom has decimated ecosystems in the state, killing thousands of marine animals and crippling industries that rely on the ocean for their livelihood.
It has contracted to one major hotspot off the Yorke Peninsula, but questions are being raised over the government's response and its insistence that it was not toxic.
ABC's Four Corners program reported on Monday that a great white shark washed up on an Adelaide beach in May 2025, prompting an email from a pathologist that raised the alarm over the "uncommon and significant finding" of brevetoxins on its gills.
Despite the finding, SA Health did not update its advice and days later Premier Peter Malinauskas declared the bloom "doesn't present a risk to people's safety".
This week, the premier said "alcohol is a toxin, and we don't run around the country saying we've got a toxic beer crisis".
On Tuesday, Liberal primary industries spokesperson Nicola Centofanti said there was now no doubt the bloom was toxic.
"I think that the people of SA deserve an apology from Peter Malinauskas for gaslighting them."
The ABC report had exposed the government knew about brevetoxins last May, yet "sat on their hands" until September to change the health advice, she said.
She wants a royal commission into the "damning and explosive" revelations.
Greens senator Sarah Hanson-Young said the government was trying to downplay the bloom's impacts for months, ahead of the March 21 state election.
"First the environmental, then the economic and now we see they haven't been upfront about the health impacts," she said.
"The full health advice must be released and an independent review completed to help restore public confidence and trust."
Liberal MP Stephen Patterson said when there was a major foam event on Adelaide beaches in August, he posted on social media a warning of the serious health effects, urging people to stay away.
"Only a day later, I received a signed letter from Health Minister (Chris) Picton accusing me of spreading misinformation," he said.
"It's quite clear that the government was spreading misinformation."
Mr Malinauskas was opposed to royal commissions being used as a "political excuse to drum up conspiracy theories", saying what was needed was decisions based on science and research.
He said he knew at the start of the election campaign there would be "some people bandying around conspiracy theories".
"I just didn't expect it to come from the Liberal Party and the Greens on the algal bloom," he said.
Voting for the state election began on Saturday.
More than 66,000 people voted in the first two days of early voting centres opening, SA Electoral Commission figures show.
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