The ACCC is planning a crackdown on "drip pricing" - the covert additional fees charged by online retailers and booking sites.
The consumer watchdog will look to take "enforcement action" in "the near future", says chairman Rod Sims.
Drip pricing describes the practice of adding fees and charges to online purchases above the advertised price.
The charges, which can include shipping and handling costs, often appear late in the transaction process. They differ from upselling in that they are essential to the product on offer.
Airlines are notorious for it, frequently charging extra fees for luggage and insurance.
"Anyone who has gone online to buy an airfare or ticket to the football will be aware of `drip pricing'," Mr Sims said.
In an interview with the ABC on Friday, he stopped short of accusing companies of breaching the law in their drip pricing practices.
But he said some are "really pushing the limits".
The ACCC has a range of powers under competition and consumer laws. It can issue infringement notices and accept court enforceable undertakings from companies to improve their compliance.
It can also take companies to court.
In a Friday statement, the ACCC outlined a range of other priorities for 2014, including cracking down on misleading carbon pricing representations and door-to-door selling.
