MINIBUS services on Hong Kong Island would have to improve in the face of competition from new franchise operator Citybus, a transport official warned yesterday. Speaking on his last day as Assistant Commissioner for Transport before retiring, Richard Meakin said some minibus commuters were likely to be lured to the new Citybus routes. Citybus last week began operating on 26 Hong Kong Island routes and was likely to attract customers from both red and green minibus services, Mr Meakin said. Red minibus operators, which he described as the most ''market-sensitive'', had already asked to expand. But there would not be a major overhaul of the Government's policy on gradually reducing the number of red minibuses and operators would have to exploit areas of improvement within existing constraints. Green minibuses, despite their monopoly on certain routes, would also be forced to provide cleaner and more air-conditioned vehicles. Mr Meakin said the lack of com petition on green minibus routes had resulted in a lack of improvement. But operators could expect challenges from the new franchised bus operator, which was more aggressive and boasted a customer-orientated service.