One in every 12 vehicles checked for emissions fraud devices were discovered to be fitted with one during four months of checks by the DVSA.
Of 3,735 trucks stopped and searched by the DVSA between August and the end of November last year, 293 (8%) contained cheat devices such as AdBlue emulators.
DVSA declared it would be conducting the roadside searches last June in a bid to crack down on rogue operators using the devices to cut operating costs.
The agency found that of the 1,784 vehicles registered from mainland Britain that were checked, 151 (or 8.5%) were fitted with emission cheat devices.
DVSA also stopped 1,657 vehicles from outside of the UK, 82 of which contained the cheat devices (5%).
While just 294 trucks from Northern Ireland were stopped, 60 of these (20%) were found to have devices fitted, a fact singled out by DVSA in their report.
Hauliers discovered using a cheat device were given 10 days to remove them or face a £300 fine.
DVSA said it will also visit 100 operator sites to check the rest of their fleets are compliant, and that it had already passed multiple cases to the traffic commissioners.
The government body said that owing to the "success" of the searches last year, it will introduce new search locations in the UK this spring.
DVSA chief executive Gareth Llewellyn “DVSA’s priority is to protect you from unsafe drivers and vehicles. We are committed to taking dangerous lorries off Britain’s roads. Stopping emissions fraud is a vital part of that.
“Anyone who flouts the law is putting the quality of our air and the health of vulnerable people, at risk. We won’t hesitate to take action against these drivers, operators and vehicles.”
Senior traffic commissioner Richard Turfitt said the “traffic commissioners welcome the steps being taken by the enforcement agency to identify emissions cheats. Use of these devices threatens to undercut responsible and compliant operators as well as damaging the environment and public health”.
"We will look to take action wherever an operator seeks an unfair and illegal advantage over the rest of industry," he added.
When the campaign was announced last June, truck manufacturers voiced concern that it would be hard to catch offenders in the act using the devices because some of them were easy to remove quickly.
Ross Paterson, head of product and marketing at Mercedes-Benz Trucks UK, told CM: I am not sure how easy it will be to catch offenders at roadside checks as all the driver needs to do is unplug it from under the dashboard."
Martin Flach, product director at Iveco, echoed his sentiment: "Having seen the physical device, it is small enough to hide behind the dash and would be difficult to find."
However the move to crack down o the use of cheat devices, which increase vehicles' NOX emissions, was widely welcomed by the industry.
Transport consultant and then-policy director at the RHA Jack Semple said: "This is a shocking practice that needs to be eradicated. Any move to stop people cheating the system is welcome."