The Government has defended the upcoming changes to the Certificate of Entitlement (COE) system, saying the use of engine power to differentiate mass market cars from luxury models allows for better rule enforcement and compliance.

The new COE rules, which will take effect next February, stipulate a capping of brake horsepower for Category A cars at 130bhp on top of the existing requirement that limits the engine capacity of these cars to 1,600cc.

Transport Minister Lui Tuck Yew said on Friday: "We have chosen something which I believe is more simple, more stable, easier and more straightforward to implement and to police."

Since the announcement on Monday last week, some have asked why open market value (OMV) or carbon emission was not used instead of engine power to differentiate luxury and mass-market cars.

Mr Lui said the authorities had considered "very carefully" the use of OMV as a parameter. But he said the value is subject to fluctuations due to factors such as currency movements and cars of different origins.