The Australian Competition and Consumer Commission is taking legal action against makers of laundry detergent for price fixing.
It says the makers of detergents including Omo, Cold Power and Radiant have been colluding to deny consumers cost savings.
The ACCC says Colgate Palmolive, Cussons and Unilever Australia entered into agreements in 2009 to use only ultra concentrate laundry detergents, but still charged the same price as standard concentrate products that are more expensive to produce
It said Woolworths was also aware of this behaviour, playing a key role in organising the transition to the new products and the introduction of anti-competitive pricing.
AAP reports the ACCC has begun civil proceedings against Colgate, Cussons and Woolworths in the Federal Court in Sydney.
"Ultra concentrate detergents are cheaper to produce, store and transport," ACCC chairman Rod Sims said in a statement.
"The ACCC alleges that this offered significant cost savings which, by agreement, were not passed onto consumers.
"These alleged arrangements also standardised the ultra concentrate products offered, denying consumers a variety of choices on pricing, package volumes and the strength of the concentrate product."
When similar products were launched in New Zealand, consumers were offered significant discounts, the ACCC said.
AAP reports Unilever and its employees have been granted conditional immunity from the ACCC's legal proceedings after the company came forward with information about the alleged conduct matter.