Covert cameras that bust motorists using their mobile phones behind the wheel are set to begin dishing out $1000 fines to drivers from October.

New figures have revealed the cameras caught out more than 15,000 potential mobile phone offences during a six-month trial that wrapped up in December.

It means the Government could have raked in over $15 million if fines had actually been issued.

The technology also detected more than 2200 potential seatbelt offences, including passengers sitting in the front seat of the vehicle.

The government has revealed the cameras will be rolled out again on Queensland roads from the second half of the year, but there will be a three-month grace period where motorists will only get warnings.

From October, the cameras are then expected to slap offending drivers with fines - which includes the $1000 penalty for mobile phone use while driving.

The Department of Transport and Main Roads has warned the cameras will be in operation "anywhere, anytime".

"During the trial, we tested multiple cameras (both fixed and mobile) at multiple sites using two companies," a spokeswoman said.

"We are not releasing the testing site locations.

"The cameras will be rolled out in the second half of 2021, with the first three months of operation sending warning notices to potential offenders, before infringement notices are issued."

Treasury coffers are set to rake in a massive $600 million next financial year from all fines and forfeitures - up $140 million from 2020-21, with Budget papers revealing that the spike is "partly" due to the new cameras.

Laws have already passed the parliament that allow authorities to issue fines to mobile phone offenders who are busted on the new cameras.

Originally published as $1k mobile phone fines about to get real