Fears of a further surge in the prices of second-hand subsidised flats arose yesterday, after the Housing Authority widened the net of eligibility by raising income and asset caps for a scheme that helped "low- and middle-income families" buy homes. The criteria were changed so even more people would qualify to vie for subsidies under the Home Ownership Scheme. When the authority last eased the rules in January 2013, sellers were spared the payment of a land premium if they sold to non-public-housing occupants - the same waiver that previously applied only when public-housing occupants were the buyers. The earlier revision had been criticised for driving up demand, with official data showing second-hand HOS flat prices up 35 per cent during the 18 months since then, though the government had maintained the rise was caused by various factors. Now, the authority intends to make more people eligible by lifting both income and asset caps in its August round of application - to HK$25,250 and HK$800,000, respectively, for singles and HK$50,500 and HK$1.6 million for families. Stanley Wong Yuen-fai, of the authority, said the limits were derived based on property market prices from January to March. "The calculations were based on the latest market data," he said yesterday. "I believe the mechanism is objective." Up to 2,500 people will be selected by ballot. Lee Wing-tat, chairman of housing-policy think tank Land Watch, said the scheme could not do much to improve home affordability as it did not increase supply, and might even backfire. "It's not the scheme per se that pushes up prices, but the market sentiment heated up by the scheme," Lee said. "As more people are now eligible to apply, competition for the flats will be further fuelled." The current means test sets the pay and asset caps at HK$21,050 and HK$415,000, respectively, for singles and HK$42,100 and HK$830,000 for families. The new income caps are substantially higher than the average pay of Hongkongers. In the first quarter of this year, median personal monthly salary and median household income stood at HK$14,000 and HK$24,900, respectively, Census and Statistics Department data showed.