PKR's Bayan Baru MP Sim Tze Tzin today questioned why a reply to his parliamentary question on Riza Aziz and Jho Low seems to be cloaked in secrecy.

Sim had asked if police have questioned Riza, who is Prime Minister Najib Abdul Razak's stepson, and businessman Low, in its 1MDB investigation.

When Sim asked during the May parliamentary sitting, if Low was questioned by cops, the Home Ministry replied that he was not.

However, this time with Riza in the mix, there was no clear answer on whether the duo were quizzed.

The written reply dated yesterday only states that police are now conducting follow up investigations on instruction of the Attorney-General's Chambers.

"To ensure that investigations are not disrupted, the ministry cannot reveal details of the investigation until it is concluded and the AG's Chambers has made a final decision over the investigation findings," the reply reads.

Sim said this is unacceptable because the duo were named in the United States Department of Justice lawsuit to recover more than US$1 billion of assets bought using funds allegedly siphoned from 1MDB.

"Why was the minister able to be transparent before but has to be secretive now?

"Is it because the question includes the name of (prime minister's wife) Rosmah (Mansor)'s son?" he asked at a press conference at the Parliament lobby.

The reply comes after Dewan Rakyat speaker Pandikar Amin Mulia said ministers need not reply to questions on the DOJ lawsuit, to avoid sub judice.

However, former Court of Appeal judge Mohd Hishamudin Mohd Yunus said the matter of sub judice does not arise as the hearing is in the US.

DAP Gelang Patah MP Lim Kit Siang said he will file a motion to seek review of Pandikar's ruling on the matter.