JAYANTA BASU A smoke-belching three-wheeler on a city road Calcutta's air will continue to be polluted by the exhaust of old autorickshaws running on adulterated fuel with the government putting the brakes on the conversion of two-stroke three-wheelers to LPG. After advocating conversion for five years, the government found "demerits' in the process. It has adopted a two-pronged strategy of replacing old two-stroke autos with four-stroke ones and penalising the thousands of illegal three-wheelers. Transport minister Subhas Chakraborty, senior officers of Calcutta police and state police and government officials met at Writers' Buildings on Monday to discuss the penal measures. "The department is not in favour of conversion as we have found lots of demerits in old autos switching to LPG. Instead, we are planning to replace them with new ones and also catch the illegal autos,' said Ranjit Maity, the joint secretary of the transport department. Though both two-stroke and four-stroke autos are converted to LPG throughout the country, the Citu-controlled autorickshaw union in Bengal has long been arguing against conversion. According to sources, the decision to stop conversion was taken in a meeting at Writers' recently. It was attended by Chakraborty, environment minister Sailen Sarkar, labour minister Anadi Shaw, who represented the auto union, and senior officials of the transport and environment departments. Owners of two-stroke autos can take loans from banks to buy four-stroke vehicles after depositing Rs 30,000 as seed money. Out of it, Rs 10,000 will be provided by the government as subsidy and Rs 8,000 will come from selling the old vehicle. A new four-stroke auto costs about Rs 1.3 lakh. "We have received a proposal from the state government to replace old two-stroke autos with four-stroke ones. The government is even prepared to provide some subsidy. We will consider the proposal once the details are worked out,' said Kishore Ghosh, the secretary of the Citu-controlled autorickshaw union. He made it clear that "there is no question of conversion to LPG now'. The green lobby smells a rat in the government's u-turn. "How can auto owners who could not convert to LPG by spending a few thousand rupees buy new vehicles by spending over a lakh?' asked environment activist Subhas Dutta. "The central surface transport ministry promoted conversion of autos on the basis of clearances by the Automotive Research Association of India and Vehicle Research Development Establishment,' said environment expert S.M. Ghosh. Autos have been successfully converted to LPG in cities like Bangalore and Chennai, pointed out Anumita Roy Choudhury of the Delhi-based Centre for Science and Environment.