BUSINESSMAN Oei Hong Leong has hit back at claims made by Citibank over his foreign exchange losses as the legal battle between the tycoon and the US banking giant goes up a gear.

Mr Oei's reply to the Citibank defence filed a fortnight ago centred on a few key points, including the bank's contention that it could not be responsible for losses racked up by such a highly sophisticated investor making his own investment decisions.

In his reply filed with the High Court on Tuesday, Mr Oei said that this was irrelevant as he was not disputing that he is a highly experienced investor.

'I have been a private banking customer with Citibank for about 30 years,' he said.

Instead, he is arguing that he had depended on Citibank to provide him with accurate and reliable information about his margin positions to aid him in his trading decisions.

In particular, he is alleging that the bank's inclusion of a certain US$50 million (S$72 million) sum in his trading lines had misled him about his trading exposure.

Mr Oei launched his suit against Citibank for negligent mistatement and misrepresentation in May. He claims that he lost $1 billion on his forex investments as a result of this lack of reliable information. He has settled all outstanding amounts with the bank.

Mr Oei invested in various foreign exchange contracts on margins, meaning that he needed only to stump up in collateral a fraction of the total outstanding amount of his trades.

The value of such contracts fluctuated daily, depending on how the currencies moved. The bank calculated the value of all these contracts daily and worked out a total value.

Based on collateral that he placed with Citibank, Mr Oei would have had to top up more funds to maintain the margin level or he may have had a surplus. Individual investors would not normally have the tools to calculate the value of such contracts.

Read the full report in Thursday's edition of The Straits Times' Money.