UPDATED 5.58PM | Former treasury secretary-general Irwan Serigar Abdullah has denied Finance Minister Lim Guan Eng's claims that the previous BN government had pilfered RM18 billion meant for goods and services tax (GST) refunds.

Instead, Irwan said, the money was placed in government-consolidated funds and that amounts due for refund were deposited into trust accounts on a monthly basis, based on the requirements of the Customs Department.

"I believe this information is available from the Accountant-General's Department and the fiscal division of the MOF," he was quoted as saying by The Star.

Irwan was responding to Lim's allegations yesterday that the government had misused RM18 billion out of RM19.4 billion in GST refunds that had been collected since the tax was first implemented.

Lim claimed the funds were used to cover up deficits, finance development projects and to "do as they wished".

The alleged shortfall also reportedly led to a delay in refund payouts.

Lim: Show me the money

In an immediate response, Lim told reporters that Irwan should disclose where the money had gone.

"It's not there; if it's there then we would have paid back by now. (But) It's not there.

"If Irwan says it is there, we want him to tell us where is it hidden. Perhaps he knows something that all of us don't.

"He must have hidden it somewhere. Where he hid it then, as a former Treasury secretary-general, that's all we want to know," Lim told reporters at the Parliament lobby today when questioned.

Additional reporting by Shakira Buang.