China's biggest brokerage firm, Citic Securities, overstated its underlying business by a whopping $166 billion (£110bn), the country's securities association has said.

The Securities Association of China said the brokerage overstated the amounts of its equity swap transactions in its October report.

Citic said the error was made, between April and September, due to a system upgrade and has now been amended. But investigations led to some executives admitting insider trading. In September, Citic's shares tumbled after it was reported that three executives, including its president, were under police investigation.

Chinese regulators have made real efforts to crackdown on suspicious trading since its stock markets plunged in the summer. The China Securities Regulatory Commission said it would investigate Citic's error, and take further action if necessary.

Citic's shares fell by around 1% following the news.