The Rembau MP said he wanted the allegation by Lim Guan Eng “investigated and substantiated”, otherwise it would be left as sensational headlines without any evidence being presented.

He said the minister’s speech in Parliament on the missing tax refunds or input tax was devoid of a detailed breakdown of the unpaid claims.

“I do not think an internal inquiry by the finance ministry is sufficient when such a serious allegation of misappropriation has been made.

“Since the minister is not keen on anything beyond an internal inquiry for now, I will nudge this along in the public’s interest,” he said on Twitter.

Lim told the Dewan Rakyat yesterday that about RM18 billion in GST input tax, which was supposed to be paid back to businesses since the implementation of the tax in 2015, was missing.

He said RM19.4 billion had not been refunded to businesses because the former Barisan Nasional government had misappropriated the funds.

The funds were supposed to be put in a trust account but instead went into the consolidated fund and were spent, he said.

Only about RM1.5 billion remained in the account, he said during the second reading of the bill to repeal the GST.

Lim declined comment when questioned yesterday if former prime minister Najib Razak was implicated in the “stolen” funds.

“Najib is already facing multiple charges, so I don’t want to comment on this until the investigations are completed,” he said at the Parliament lobby.

Lim also claimed that a former Treasury secretary-general was likely aware of the shortfall in the GST refund trust account.