LEGISLATORS yesterday warned the taxi industry that services must improve if further fare increases are to be approved. The comment came as legislators backed the Transport Advisory Committee's (TAC) recommendation to increase taxi fares by an average of 17.7 per cent from mid-November. They specifically warned drivers against picking and choosing passengers, overcharging and increasing fares on public holidays and during typhoons. Police have begun a crackdown on such malpractices and yesterday arrested 10 drivers for meter-tampering. Liberal Party legislator Selina Chow Liang Shuk-yee said: ''It seems that we can only express our grievances about poor taxi services whenever the taxi drivers apply for a fare increase. ''But, once we approve the fare rise, we are back to the situation where we can do little to improve services.'' Pro-China legislator Tam Yiu-chung urged the Government to monitor taxi services. Legislators endorsed the TAC recommendations given that taxi fares had not been increased since January 1992. Under the recommended rate, the flagfall, covering the first two kilometres, would increase from $9 to $11.50 and the charge for every subsequent 200 metres would go up from 90 cents to $1. The fare increase package is expected to go to the Executive Council later this month before being tabled in the Legislative Council. Yesterday's police operation was the fourth in the effort to improve taxi services. The drivers were detained when radios in their taxis were found connected to unlicensed channels. Police believe the channels matched the pulse frequency controlling meters, thereby allowing the drivers to speed up their meters. The taxis were cruising with out-of-service signs and were stopped at a roadblock at Kowloon Park Drive, Tsim Sha Tsui. A tamper-proof taxi meter introduced by the Transport Department last year had proved unpopular, according to motor vehicle examiner Donald Tsang Man-wai. He said the department had backed away from making it compulsory for taxi operators to replace old meters because of high costs. But operators would have to allow government engineers to modify the old meters to prevent tampering by the end of this month. The Secretary for Transport, Yeung Kai-yin, said the Government was waiting for a TAC report for an overall review of services. He also revealed the Government was considering drawing up standardised criteria on factors such as inflation and operation costs for future fare increases.