A tax concession for environmentally friendly cars may be increased to lessen the impact of the proposed steep rise in the first registration tax for vehicles. The government proposes raising the concession for 43 brands of green cars from 30 per cent, or no more than HK$50,000 of the tax payable, to 45 per cent or no more than HK$75,000. It is the latest response to calls for leniency from lawmakers scrutinising a bill to increase the car tax by 15 per cent to curb private vehicle growth and traffic congestion. The Transport and Housing Bureau said the number of vehicles increased 5.4 per cent last year - the highest in 14 years - and average speeds were reduced on major roads. But the lawmakers said the increase in tax could dissuade buyers from switching to green vehicles because it made them too expensive. The government has already agreed not to charge the new tax rate on purchases made before the rise came into force on February 23 when Financial Secretary John Tsang Chun-wah made his budget speech. About 6,000 new car buyers might benefit from the proposed exemption. The bureau said the extra concession could encourage those who had decided to buy a car or replace their old cars to choose greener cars. Friends of the Earth director Edwin Lau Che-feng questioned whether the concession was in conflict with the original objective of the registration increase. 'If you want to suppress car growth, it is definitely not the way to go,' he said. Instead, Lau said there should be a policy to force old and polluting cars off the road, such as increasing the frequency of vehicle tests on such cars from once to twice a year. He said the government could also promote the use of public transport or better traffic management to reduce congestion.