IMMIGRATION staff will be diverted to Kai Tak airport from other entry points at times of extreme demand despite the Government's appointment of more than 150 staff to the department. Immigration Department director Laurence Leung Ming-yin yesterday admitted he was under-staffed and had only received about half the number of new staff necessary to maintain optimum control levels at checkpoints throughout the territory. His concerns also sparked fears that the staff shortages could lead to growing numbers of undesirables entering the territory. Security Panel chairman Selina Chow Liang Shuk-yee said the shortage of officers at entry points not only caused delays but put pressure on officers to process people quickly, and as a result the scrutiny of people entering the territory was poor. Mr Leung said government approval for 157 more posts for 1994/95 was welcome, but it was the first staff boost since 1989 and in that time there had been huge increases in traffic at land crossing points and at Kai Tak. ''We will continue to get by but we may have to employ people at the airport on an emergency basis from elsewhere if demand from time to time becomes too heavy.'' Mrs Chow said she was ''not at all happy'' with staffing levels and said the security of Hong Kong should be given priority. ''We are only talking about an extra 150 staff or so to make a difference - not too much to ask at a time when the Government is flush with cash,'' she said. The Immigration Department is also considering tougher penalties for employers found to be hiring illegal immigrants. Mr Leung said Hong Kong employers were continuing to take advantage of the cheap labour market offered by illegal workers despite the existing penalties. Legislation presently provides for fines of up to $250,000 and imprisonment for three years. A taskforce of 46 officers will be established later this year with one of its main functions being to mount large-scale field operations against illegal workers and overstayers. Mr Leung said talks with representatives from the governments of India, Pakistan and Bangladesh where many illegal workers came from would also be stepped up. He said several areas of responsibility for immigration would continue to grow during 1994. One of the main areas of growth, he said, would be in the processing of British Nationality (Overseas) passport applications. He said a backlog of 128,000 applications had prompted him to request additional resources to deal with the workload. Moves are also in place to expedite the processing of people passing through Lowu checkpoint. Mr Leung said an extra 72 staff would be assigned to Lowu during Lunar New Year to cope with the expected large numbers crossing the border. He said computerised identification equipment to be installed at Lowu would also improve the flow. An extension project is under way to increase the existing 88 immigration counters to 160. Mr Leung said he also hoped to be involved in talks with China over the issue of Special Administrative Region (SAR) passports. ''I would be prepared to go to Beijing if necessary to discuss the SAR passports with China and attempt to resolve how it will be done,'' Mr Leung said. ''At this stage we have not had an offer from China to go and discuss the issue.''