THE Independent Commission Against Corruption's (ICAC) prosecution and conviction records have reached a three-year high, but its head of operations said reports and intelligence suggested corruption was still increasing. The ICAC released statistics on prosecution and conviction rates to counter lawyers' claims that its anti-corruption efforts had fallen short in court. The lawyers said the ICAC had lost convictions in a number of drawn-out trials which had cost taxpayers millions. One lawyer said recent ICAC claims about triad activity and widespread malpractice in the legal profession could be based on ''sour grapes'' because of the ICAC's ''low rate of success''. However, the ICAC released statistics which showed its conviction rate had risen to a three-year high of 80 per cent last year or 253 convictions, from 64 per cent the previous year. The conviction rate for 1990 was 70 per cent. ICAC Director of Operations, Mr Jim Buckle, said the courts ultimately decided whether to convict on ICAC evidence. ''Last year the courts did so in four out of five cases and that seems to be a pretty good performance,'' he said. However, Mr Buckle said it would be wrong to believe that statistics alone could reveal the full extent of corruption. The ICAC monitored corruption reports, available intelligence, and public attitudes and perceptions to assess the problem. ''At the moment we are monitoring the situation carefully as we believe corruption may be increasing,'' Mr Buckle said. Criminology lecturer at Hongkong University's Department of Sociology, Dr Jon Vagg, said the ICAC's conviction success rate could have been related to the large number of credit card fraud syndicates taken to court by the ICAC last year. He said corruption also could be higher than statistics indicated, because they tended to be based on public reports or suspicions. ''The hallmark of corruption is secrecy so it is difficult to relate the number of reports to the actual amount of corruption, but it is widely believed that corruption is increasing. ''It is also widely believed that it will escalate with the approach of 1997 as people try to make as much money for themselves as they can.'' The number of corruption complaints which the ICAC felt it could pursue had decreased from 1,759 in 1991 to 1,679 last year. The number of people charged by the ICAC was 337 last year - four more than the year before. Prosecutions of police increased slightly from eight in 1991 to nine last year. Prosecutions of people from public bodies decreased by more than half to nine, and prosecutions of officers from other government departments decreased by 32 per cent to 17. The ICAC also assured lawyers that a ''witch-hunt'' had not been instigated to find people to back claims of triad activity and widespread malpractice in the profession. Some lawyers have expressed concern the ICAC had exaggerated problems because it had been thwarted by lawyers in major trials. An ICAC spokeswoman said: ''The ICAC does not favour criminalising touting or fee-splitting arrangements that are not corrupt; these should be left to the profession to deal with. There is no 'witchhunt'.'' She said the ICAC had offered to help the Law Society and the Bar Association tackle problems by helping devise audit measures; publicising the dangers of touting; and providing information that does not breach confidentiality of its sources of information.