A TOP legislator has been accused of having a 'substantial conflict of interest' for his role in a showpiece Housing Department project in Ma On Shan which has run into severe ground condition problems. The Liberal Party's Edward Ho Sing-tin is chairman of the authority's building committee and senior partner in Wong Tung & Partners, the architectural firm which designed the waterfront development at Area 90. The revelation was made by SY Engineering, the piling contractor for phase five of the project, which is several months behind schedule after encountering underground marble caverns. On Thursday Mr Ho said the discovery of the caverns was not a valid excuse for slow progress. But the company hit back and said it was well aware of the cavities and only stopped work because it considered it too dangerous to continue after part of the site collapsed leaving a two metre hole. 'We consider Mr Ho has a substantial conflict of interest. He is chairman of the building committee; he is also a joint managing director of the consultants responsible for the management of the project,' it said. The company said any additional piling could cause further collapses, undermining housing blocks in other phases which are nearing completion. Two geotechnical consultants, including experts who advised on the Government's slope safety review, are being used by SY to carry out a thorough site investigation. 'According to the preliminary findings, to carry out work in the specified manner will cause massive loss in underground water, sand and soil forming hollows of unpredictable size. 'These hollows, in addition to the known cavities, can cause the ground to collapse at any time. It is possible subsidence of bigger magnitude would occur posing a threat to the stability and safety of nearby future residences,' the SY spokesman said. Mr Ho rejected SY's claims. 'Binnie & Partners [the consultant used by Wong Tung to design the foundations] has said categorically it is safe. [When we won Ma On Shan] I was very careful. Another partner, Robert Kessler, took care of it,' he said. Mr Ho said he declared interest or left the room if the project was discussed at committee meetings. Mr Ho said SY Engineering had successfully installed more than 100 piles, although the firm said this was nonsense. 'Only the pile casings, some of which have disappeared below the surface as a result of ground movement, have been fixed. Just 24 piles had been finished,' it said. The $356 million contract was due to end in March ready for the construction of four 36-storey housing towers. Only 20 per cent has been completed.