Photographs obtained by The Daily Advertiser show the 250-metre and 50-metre warning signs were lying on the side of the highway and not visible to drivers heading east at 11.25am on Saturday.

It is the latest breach of the government's speed camera strategy regulations by private operator Redflex in the Wagga area during the past 12 months.

In February, Roads Minister Duncan Gay admitted Redflex had committed "entrapment" when illegally conducting speed camera patrols on a city street.

Last month, the speed camera operator came under scrutiny after its vehicle parked in long, dry grass, potentially posing a bushfire risk to road users and nearby landholders.

Despite the ongoing furore, Redflex is set to continue its contract to carry out speed camera patrols.

"Redflex has a contract with RMS to carry out speeding compliance operations via the mobile speed camera program until 2016," an RMS spokeswoman said.

"Mobile speed camera operators in NSW are not paid per infringement and do not receive incentives. They receive payment based on the number of hours of enforcement they carry out."

The spokeswoman maintained speed cameras played a vital role in road safety.

"Mobile speed cameras are in place to ensure speed limit compliance and improve safety on NSW roads," she said.

Regular audits are carried out on mobile enforcement operations which include the placement of advisory signs, the spokesperson said.

The Daily Advertiser contacted the Melbourne office of Redflex for comment, but did not receive a response at the time of going to print.