THE controversial Western Harbour Crossing bill is likely to be amended with the opening tunnel toll pulled down from the original $30 to $25. But this may risk the entire tendering exercise starting over again as the only bidder for the $7.5-billion project has said it would not accept any lowering of the toll. The Liberal Party will decide today if it will put forward an amendment to lower the tunnel poll. The party's legislator Steven Poon Kwok-lim said they would await Secretary for Transport Yeung Kai-yin's reply to their query on the calculation of internal rate of return (IRR). He said they would amend the bill if Mr Yeung failed to persuade them that the proposed minimum IRR of 15 per cent, under the existing formula, was a fair rate. Mr Poon said the consortium's formula, based on dividend returned to shareholders of the company, would also allow the consortium to enjoy an IRR one or two per cent higher than the conventional practise. ''It's the first time in my entire life I've seen such a formula of calculating the IRR,'' the former general manager of China Light and Power said. He said the established practise of calculating IRR was based on net revenue earned by the company. If the 15-member party decide to go forward with the amendment, it is almost certain that the bill would be unable to remain intact as the 13-member United Democrats have already stated they would also move an amendment to lower the opening toll. The two parties can easily muster a majority to push through the amendment in the 59-member Legco as the four-member Meeting Point also opposes the $30 toll. Representative of the consortium, Gerry Higginson, told legislators last week that lowering the $30 toll would mean negotiating another deal. He warned that the consortium would withdraw from the project should Legco amend its package, arrived at after seven months of negotiation with the Government. The 30-year tunnel franchise was offered to the only bidder for the project, which comprised CITIC Hongkong, Cross-Harbour Tunnel Co Ltd, Kerry Holdings Ltd and China Merchants Holdings. But Mr Poon said he was confident a final outcome which was acceptable both to the consortium and the public could be arrived at. ''I think it's too early to say the consortium will pull out of the project,'' he said. ''They are businessmen. They will see if the amended package is profitable or not. ''The public will judge if we are doing the right thing,'' he said.