COMPLAINTS against taxi drivers in the third quarter of this year soared by almost 60 per cent over the second quarter. The increase sparked concern among legislators, who warned the taxi industry that service must improve to justify future fare increases. Figures to be revealed by the Transport Complaints Unit show it received 1,065 complaints between July and September this year, representing a 58 per cent increase from the 676 cases in the second quarter. The unit received a total of 746 complaints in the third quarter of 1992. Refusing hires accounted for 377 complaints - the largest category - which was 1.5 times more than that in the second quarter. There were 337 complaints about overcharging and 188 about drivers' misconduct. Others included soliciting passengers, failure to take the most direct route, and failure to reach the destination. The executive secretary of the Transport Complaints Unit, Leung Yiu-chung, said the increase was mainly due to a greater awareness among the public, following a recent police enforcement against taxi drivers. A spokesman for the Taxi Associations' Federation, Ng Kwok-hung, said the number of complaints in the summer was always higher than at other times. He said most complaints concerned refusal to take passengers across the harbour because drivers were worried about being unable to find a passenger for the return trip. Mr Ng said their proposal to set up taxi stands on either side of the harbour would help reduce complaints. The industry attributed poor services to low fares and claimed it had been difficult times for them since early this year when they applied for fare increases. Legislator Zachary Wong Wai-yin said the fare rise two weeks ago was a big one and exceeded the inflation rate. ''If taxi services make no improvement after the fare increase, I believe the Legislative Council will not approve an increase in the future,'' said Mr Wong, who is also vice-chairman of Legco's Transport Services Committee. On November 14, fares for urban taxis rose from $9 to $11.50 for the first two kilometres, while in the New Territories the flagfall went up from $8 and $10. Meanwhile, the public and tourists will find it easier to identity unscrupulous taxi drivers. Under the Road Traffic (Amendment) (No 4) Bill, which is expected to be passed next month, drivers are requested to display a working identity card which contains a photograph of the driver, his name and licence number.