SUN Hung Kai Properties is providing up to 90 per cent of mortgage financing in the sale of 180 garden houses at its huge residential project Palm Springs in Yuen Long. The aggressive financing approach is likely to further upset the Government, which has resolved to maintain the 70 per cent ceiling on mortgage loans, and has denounced arrangements between some banks and developers to offer extra credits to home buyers. In an apparent bid to boost sales of Palm Springs houses, Sun Hung Kai, one of the territory's biggest property developers, will provide buyers with three alternatives for mortgage loans. As well as the normal practice of getting 70 per cent mortgage loans from banks, buyers can apply to Sun Hung Kai's finance subsidiary for mortgage loans of up to 90 per cent of property value. Also, home buyers can apply for a 80 per cent mortgage if they choose a stage-payment method. This means they put up only 10 per cent of the flat value as down payment, followed by five per cent in June and five per cent in September. Mr Thomas Kwok Ping-kwong, vice-chairman and managing director of Sun Hung Kai, said that for this sale its finance subsidiary would offer mortgages at the same rate as banks. The company was trying to help those ''genuine buyers'' who could not afford the usual 30 per cent down payment, he said. ''We still hope that buyers will try to take the 70 per cent mortgage financing arrangement with banks as much as they can,'' he said. Mr Kwok added that Sun Hung Kai could better utilise its capital resources by offering extra credits to buyers, instead of putting the money in the bank and getting low returns. Mortgage lending commanded higher interest rates, compared with the relatively unattractive returns on bank deposits, he said. The ''California-style'' garden houses at Wo Shang Wai, Yuen Long, will be offered for an average of about $2,160 a square foot over the next two weeks. Mr Kwok said Sun Hung Kai had lowered the price by more than 10 per cent in order to attract buyers. He would not say if the move was linked to recent dampened sentiment in the home-buying market. But he noted that the release of Palm Springs houses was always on schedule, and Sun Hung Kai never had any intention of delaying the sale because of a weakened market. Palm Springs comprises about 1,600 garden houses and supporting commercial and community facilities. The houses range from 1,410 sq ft to 1,775 sq ft. Mr Kwok said the Hongkong Real Estate Developers' Association would propose that Government phase out controls on mortgage financing. A working group had been set up after last week's meeting with Financial Secretary Hamish Macleod to spell out concrete proposals. Mr Kwok, a member of the executive committee, said the proposal would call for a relaxation of the 70 per cent mortgage limit for first-time home buyers and genuine end-users, together with ways to prevent speculation or fuelling of property prices. Mr Macleod had dismissed an immediate relaxation of the mortgage lending policy but the association was asked to make suggestions. He said the association might wait until after Mr Macleod's March Budget speech. which is likely to contain suggestions for helping the sandwiched class buy homes.