AN economic slowdown in China would mean the withdrawal of ''hot money'' from Hongkong's stock and property markets, a brokerage predicts. G.K. Goh Securities (HK) suggests that such a slowdown might also affect investors' perceptions of the market, and particularly of stocks that have been given premium ratings because of their exposure to the Chinese market. In China Money Supply and the Hongkong Stock Market, the brokerage says retailing and some manufacturing stocks have already been affected by worries about the China economy. ''We believe that companies that have become involved in property development in China are especially vulnerable,'' it says. The brokerage believes there is a correlation between China's money supply growth and the performance of the Hongkong stock market. It says the impact of a mainland slowdown on the Hongkong economy as a whole would be far less severe, as China factories run from the territory are still mainly export-oriented, and get most of their raw materials from overseas. The report says labour costs are in yuan and forecasts they will remain fairly low because of China's high unemployment rate and the recent surge of migrants to the cities. The brokerage says Hongkong firms have placed little reliance on local Chinese banks, most of which do not deal in foreign currency or provide much working capital. ''Inflation and consequent credit contraction will therefore have limited impact on Hongkong manufacturing operations in China,'' it says. But any contraction in investment and consumer demand in China is expected to affect Hongkong re-exports, of which consumer and capital goods account for a much smaller share than outward processing. Just as the impact of rising inflation would be relatively small and short-lived, it says a slowdown in inflation in China would have little impact on Hongkong. ''Hongkong's main import from China is foodstuffs, which are less inflation-sensitive and have wide sources of available supply. The weak renminbi has also helped offset the inflationary impact of imported goods from China.'' The report says the nature of China's current boom is slightly different to that of 1985 to 1989 in that it is characterised by strong growth in fixed asset investment, huge increases in industrial output and rapid growth in money supply and credit creation. Strong consumer demand in the last economic upswing led rapidly to rising consumer prices, it says.