The Queensland government is taking legal action against Indian mining giant Adani for allegedly releasing sediment water eight times over the allowed limit into the Great Barrier Reef.
The Department of Environment and Science (DES) has charged the Adani-owned Abbot Point Bulkcoal (APBC) with breaching a temporary emissions licence over the discharge at the Abbot Point coal terminal during Cyclone Debbie in 2017.
DES alleges water released by APBC at a location called W2 was eight times the levels allowed under the licence.
"Last year APBC contested a $12,190 penalty infringement notice in relation to the discharge from W2," the department said in a statement on Wednesday.
A hearing on the matter has been set for October 23 in the Bowen Magistrates Court.
The maximum fine for the offence is $2.7 million
Environment Minister Leeanne Enoch said Queenslanders expect companies to be held to account.
"The Palaszczuk government takes environmental protection very seriously, we're doing the right thing, we've always done the right thing," she told reporters.
"The department of environment and science, as the regulator, have made this decision based on the best available legal advice and scientific advice."
She did not take questions.
It comes after two days of protests by anti-Adani activists, who criticised the government for not acting 17 months after the alleged discharge.
Demonstrators staged a courtroom scene outside parliament on Wednesday, a day after showering MPs with black confetti inside the house in a gesture meant to represent coal dust.
Speaker Curtis Pitt says the clerk of parliament will seek to have the demonstrators prosecuted under s51 of the Parliamentary Services Act and a review of parliamentary security is also underway.
Greens MP Michael Berkman has welcomed the prosecution.
"We're long overdue to see some really strong action from the government against this company," he said.
"We know that they can't be trusted, their track record overseas is atrocious and I'm really glad to see this step being taken," he said.
Liberal National Party shadow environment spokesman David Crisafulli said he would question the government over the timing of its prosecution at Parliament on Thursday.
"What I would hate to see is if this has been a decision that has been reached by political pressure because a few lunatics sprinkled confetti from the gallery," he said.
"If that has happened then we've lost the plot in the way we govern."
A deadline allowing the government to take legal action was due to run out on Friday.