LEGISLATORS are angry that the Secretary of the Treasury, Donald Tsang Yam-kuen, will be unable to attend tomorrow's Public Accounts Committee (PAC) hearing on the controversial sale of a Garden Road site. The hearing is considered an important one by members. About six witnesses will attend. The PAC has stepped up its scrutiny of the sale of the site which the Director of Audit Brian Jenney said reflected a loophole in government procedures. It is understood that Mr Tsang told PAC members he could not attend because it clashed with a briefing to other members on the new financing proposals for Chek Lap Kok airport. Instead, his deputy, Kwong Ki-chi, will represent the Finance Branch in appearing before the PAC. While the date for the hearing was fixed about a month ago, the date for the airport sub-committee was decided recently. Mr Tsang wrote to the committee on December 29, saying his branch would be pleased to answer members' questions over why the Central Tender Board awarded the site to the highest bidder, Hutchison Whampoa. Four of the seven PAC members also sit on the airport finance sub-committee. Some legislators suspected the airport meeting was arranged to coincide with the PAC hearing. Mr Jenney said in his report that a loophole in the conditions of sale of the site allowed Hutchison to build a 31-storey complex, five times bigger than the low-rise structure the Government intended. Those appearing before the hearing would include Peter Lo, Hutchison Estate Agents' general manager; Robert Pope, the Director of Lands; and his predecessor Chau Cham-son. Mr Tsang had told members he did not consider it was appropriate for them to invite the Director of Civil Engineering, Dr Edward Brand, to the meeting because he only stood in for Dr Nip Kam-fan, the then Director of Civil Engineering at the February 1989 Central Tender Board meeting. He also said that as board members did not keep copies of tender reports approved by the board, it would be difficult for them to recall one of the 28 cases considered at a meeting five years ago. His views were echoed by John Yaxley, who was then the board's chairman. ''However, bearing in mind the size of the highest bid in relation to the other bids and the usual diligence with which members performed their duties, I would be surprised if this disparity was not observed and discussed before the decision, as recorded, was made,'' Mr Yaxley said. Hutchison Whampoa's bid for the site was more than double the second highest bid.