Two fuel stations in the Greater Darwin area are facing nearly $20,000 in fines each for allegedly charging motorists more for fuel at the bowser than advertised, following compliance checks by NT Consumer Affairs.

The consumer watchdog completed 858 MyFuel NT compliance checks on Territory fuel stations between March 31 and June 7, issuing eight “show cause” notices and the two infringement notices.

The infringement notices of $18,958 each, were issued to a station in “Darwin/Berrimah” and another station in Palmerston, which the government said were both national chain outlets, but said it could not name the retailers “as enforcement action remains ongoing”.

It also did not explain why the larger prescribed penalty of $94,500 for misleading on fuel prices was not sought for the corporation.

A government statement said one of the outlets had advertised diesel at 229.9 cents per litre on MyFuel NT, while it charged motorists 231.9 cents at the pump.

The government said the incorrect price was displayed for six hours and was discovered during a compliance check on June 1. It added a separate breach occurred by the same national chain in Palmerston.

Treasurer Bill Yan announced in March that the NT Government would enliven an old Act called the Price Exploitation Prevention Act that would allow the NT Government to demand fuel retailers in the Territory provide their full “cost structure” to prove they are not ripping off customers, which he said was an “unprecedented move to manage the ongoing fuel crisis”.

It also claimed at the time the Act would allow the government to set fuel prices in “the most extreme cases”.

But the old Act had nothing to do with the infringement notices being issued this week and the government has not provided any update on what has occurred under that legislation, which sets higher fines of up to $74,000 for retailers who fail to comply.

Instead, Attorney-General Marie-Clare Boothby issued a press release on Wednesday about the infringement notices issued by the Consumer Affairs Commissioner, while claiming she has “slammed dodgy business practices by fuel retailers”.

“As a CLP Government, we won’t tolerate dodgy fuel pricing, and these two infringement notices show that we’re taking this seriously,” Ms Boothby said.

“I introduced this fuel price lock because everyday Territorians deserve certainty at the bowser.”

The infringements issued were issued under the Consumer Affairs and Fair Trading Regulation, which was amended in April to lock in fuel prices for 24 hours, meaning fuel retailers can set the price between 8:30am and 2pm for the following day, with that price advertised to then take effect from 6am for 24 hours.

Ms Boothby did not explain why the two fuel stations were charged the smaller “individual” fine of $18,900 and not the larger $94,500 fine for corporations under the fair trading regulations.