THE police force's top civilian staff member will step down at the end of this month to make way for a local replacement. But administrative officer Martin Lewis will continue to receive his more than $100,000-per-month salary and enjoy associated perks including accommodation until May 22 next year. Mr Lewis, who has held his present position since April 1992 and has been an employee of the Hong Kong Government since April 1974, will also receive a substantial ''golden handshake'' and a generous pension. The precise size of the payout has not been disclosed. The former Planning, Environment and Lands Branch officer refused to comment on his departure. He is 55 while the normal retirement age is 57. But it is understood Mr Lewis fought bitterly against recent plans to restructure the senior management of the force - changes that would have meant the abolition of his post. As an administrative officer, reporting directly to the Commissioner of Police, his responsibilities included civilian personnel matters, financial revenue and spending, associated monitoring and control systems, stores, and the maintenance division, which controls procurement and storage of equipment. A police spokesman confirmed a local replacement had been appointed and would start before the end of the month. The spokesman said he did not know Mr Lewis' exact salary but officials of his grade were normally given a wage in the range of between $101,000 and $118,150 per month. He was entitled to 55.5 days annual leave, free return travel to Britain, free housing and free education for his children.