Importing cars from the UK is devaluing Irish cars and putting jobs at risk, according to the motor industry.
It is warning the Government that it needs to clamp down on the volume of vehicle imports.
Since the Brexit referendum three years ago - new car sales have gone down, while imports have soared to record levels.
SIMI director Brian Cooke says imports are devaluing Irish cars.
"The customer's Irish used car is worth less, if they want to trade up they actually have to pay more," said Mr Cooke.
"That's discouraging people from entering the new car market."
SIMI is calling on the Government to bring in measures that would discourage importing and to not increase the tax on new cars in the budget.
Mr Cooke said that they have made a number of suggestions to the Finance Minister ahead of the budget next month.
"We mentioned the diesel surcharge last year that should be replaced by a charge on older cars that actually focuses on the emissions coming from those cars," said Mr Cooke.
"The diesel surcharge that was brought in last year did the opposite, it has increased the tax by a greater amount on a new car which has less emissions than an older car."
Economist Jim Power says any tax hike alongside a no-deal Brexit is sure to cost jobs.
"I could certainly see up to 10,000 - that's roughly a quarter of the jobs in the motor industry under serious threat," said Mr Power.
The motor industry is also arguing that the Government's push towards electric vehicles is pointless, if they continue to allow the importation of older, higher emission cars to be so attractive to drivers.