THERE are a number of misconceptions in Mark Lin's letter (South China Morning Post, September 22) on localisation. First, let me clarify that most civil servants are employed on either a pensionable or a contract basis. Within each category, individuals are employed on either local or overseas conditions of service, depending on their background. However, for many years, we have given preference to recruiting candidates with a local background. Those on local conditions now constitute 98.8 per cent of the Civil Service. When an individual's contract is going to expire, we look at a number of factors before deciding whether to offer him or her another contract. The main considerations are whether there is a continued need for the person's services, his or her performanceon the job and physical fitness. These criteria apply equally to staff employed on local and overseas conditions of service. In addition, however, before we will renew any contract on overseas conditions we consider whether we have anyone in the service on local conditions available to replace the ''overseas officer''. This criterion is an important part of the localisation policy. We regularly do not renew contracts, whether on ground of localisation or performance or simply because we do not need the services of the person concerned any longer. There is no question, as Mr Lin alleges, of guaranteeing continued employment to contract officers, and this applies equally to those on overseas and local conditions of service. A difficult area arose however when it came to applying the localisation criterion to the small number of contract staff on overseas conditions who had become permanent residents of Hong Kong. In this situation, the application of the localisation policycould result in one permanent resident being replaced by another permanent resident, purely because of a difference in their conditions of service. This would hardly provide equal access to the public service for all permanent residents, as required by theBill of Rights. We have therefore said that we will not apply the localisation criterion to permanent residents. But if (and I stress if) a permanent resident now on overseas conditions is offered further employment (after we have carefully considered all the criteria),this must be on local conditions. The person concerned, as a permanent resident, will have to give up any ''expatriate perks''. I can assure Mr Lin that we have taken this action only after a thorough study of the legal position. As the Association of Expatriate Civil Servants knows only too well, we strongly resisted the arguments they put forward over many months. But having reached our conclusion, we felt that it would have been irresponsible simply to wait to be taken to court as Mr Lin suggests. The public rightly expects us to take our responsibilities under the Bill of Rights seriously. In his letter Mr Lin has implied that the instructions to counsel to advise were tailored to ensure that the advice supported the change in policy. In fact the legal advice was obtained before any change in policy was contemplated. I can assure Mr Lin that the localisation policy remains in force and will continue to be firmly applied. S. W. HARBINSON for Secretary for the Civil Service The only effect of the recent change is in relation to permanent residents of Hong Kong who satisfy all the criteria for both renewal of contract and for transfer to local terms.