Several parties have come out in opposition to the Government's decision to use engine power as a criterion for the certificate of entitlement (COE) system, which they say punishes cars with more efficient engines.
In a Facebook post on Sunday, MP Hri Kumar Nair (Bishan-Toa Payoh GRC) said differentiating cars by engine capacities and power output is "meaningless" as this disadvantages more efficient cars.
He favours promoting cleaner, more energy efficient cars and suggested allocating more COEs to such cars and bringing down their prices to make them more affordable than less efficient ones.
The Land Transport Authority (LTA) announced last week that from next February, only cars with 130bhp or less fall into Category A. This criterion is on top of the existing criteria that limits Cat A cars to a maximum engine capacity of 1,600cc. This is to disqualify more powerful luxury cars, which are crowding out lower-priced mass market ones.
But setting limits on engine power discriminates against technology, said Mr Klaus Landhaeusser, regional head at leading automotive parts supplier Robert Bosch (South-east Asia).
As automotive technology advances, it is inevitable that engine power and torque increases while fuel consumption and emissions go down as a result, he said.
Models that will no longer qualify for Cat A include the Volkswagen Jetta 1.4 TSI, which has an engine capacity of 1,390cc and 158bhp and a lower emission.
One risk of using engine power is that dealers may bring in models from other markets that have older technology, higher emissions and lower power, he added.
He suggested using emissions to categorise vehicles, and allocating more COEs for cleaner cars, thus automatically favouring lower-emission, smaller cars, he said.
Asian Clean Fuels Association executive director Clarence Woo expressed concern that putting less-efficient cars on the road would affect carbon reduction and pollution control.
Singapore Environment Council executive director Jose Raymond noted that while the changes might ensure greater equity, "we should not be discouraging manufacturers which have found ways to make their engines cleaner and yet more powerful".
In response, the LTA said using fuel efficiency and carbon emissions could end up penalising mass-market models. It noted these factors are accounted for under the Carbon Emissions-based Vehicle Scheme (CEVS), which offers rebates for or taxes vehicles based on their emissions.
In his post, Mr Hri Kumar also slammed the changes as "an act of appeasement" to lower COE prices for Cat A cars. Government Parliamentary Committee for Transport member Lim Biow Chuan agreed the tweaks were not ideal. But he would prefer using open market value (OMV) to categorise cars instead of emissions.
He said: "The OMV of most luxury cars are way above $20,000. But the LTA looked at engine power instead. Will manufacturers decide to make less efficient cars?"