The stock market's controversial closing auction session was suspended yesterday after less than a year following complaints about unusual price movements in the final seconds of trading, most recently a stunning drop in HSBC Holdings shares. Hong Kong Exchanges and Clearing suspended the system for an undefined period and will start using the previous closing system on Monday. Turnover during the final 10-minute auction yesterday was an unremarkable HK$2.4 billion, compared with total trading during the day of HK$43.8 billion. On March 9, HSBC fell a further 12.47 per cent to HK$33 in the last four seconds of the auction session, dragging the shares to their lowest close since May 1995. The unusual price movement revived strong criticism and complaints from market participants, who said the system was unfair to retail investors and created an opportunity to manipulate trading. HKEx announced the suspension of the auction system three days later. Early on, lawmakers and investors blamed the system for distorting prices. A week after its formal launch, amid a rebalancing of the MSCI index, several mid-cap stocks traded abnormally high in the closing auction when more than HK$15 billion was injected into the market within 10 minutes. Legislator Chim Pui-chung, who represents brokers, said the stock exchange should have suspended the system much earlier. 'A few days after the auction system was launched, we saw a chaotic scene amid the index rebalancing,' Mr Chim said. 'Many brokers urged me to call for the exchange to suspend the system pending a review, and I did. Unfortunately, the stock exchange insisted on keeping the system until now.' The closing auction session was introduced in May last year, extending trading hours by 10 minutes and allowing investors to determine closing prices through the use of tenders. The settlement price was determined by the price level that had the highest trading volume, replacing the old method of using the middle price of the last five orders. Hong Kong Stockbrokers Association chairman Kenny Lee Yiu-sun said the closing auction system had many defects. 'It is better to use the old way to close the market,' Mr Lee said. 'There may still be some investors who try to manipulate the closing prices in the old system. But at least, the SFC is familiar with all the old tricks for it to crack down on manipulations.' Sun Hung Kai Financial executive director Joseph Tong Tang said it was not necessary to bring the suspended auction system back. 'As the past 10 months' experience has shown, the auction system has no benefit but only creates trouble. There was no reason to create the system in the first place,' Mr Tong said.