Three executives of a government cleaning contractor and a sub-contractor went on trial yesterday accused of extorting $1.9 million in government-paid wages from their workers. The District Court heard the workers had to give rebates of 12 to 32.2 per cent of their salaries to their bosses. Au Wai-hung, 45, Leung Chi-keung, 38, Chung Yuk-ki, 39, and So Wai-hung, 46, each pleaded not guilty to two counts of conspiracy to defraud. The court heard that Au, Leung and Chung were managers of Polyking Services, a subsidiary of the listed Allied Group. Prosecutor Christopher Coghlan said Polyking obtained two contracts worth $27.22 million from the Leisure and Cultural Services Department in July 2002 and November 2003. The contracts were for cleaning the Central Library and Kowloon Park. The company later awarded the park contract to So, who is accused of conspiring with the other three to provide false debit notes, statements and certificates. Mr Coghlan said the contracts stated that the workers be paid minimum salaries ranging from $3,228 to $5,190 a month. But after first being paid the full amount, the workers were forced to pay rebates before receiving their next payments. These payments ranged from 12 to 22.5 per cent and as much as 32.2 per cent if the recruit was mentally handicapped. When the department inquired into the rebates in August 2003, Mr Coghlan said, the four defendants said it was money owed by the workers to the company for training, housing allowances and meals. But he said there were no such benefits and the so-called training amounted to nothing more than a video on precautionary measures to take while cleaning that was provided by the Labour Department. Four of Au's subordinates, who allegedly assisted in carrying out the exploitation, will testify under immunity today.