PARLIAMENT Deputy speaker Ronald Kiandee has refused to make a ruling to stop the police from questioning former second finance minister Ahmad Husni Hanadzlah (BN-Tambun) for allegedly breaking his ministerial oath of secrecy.

Lim Guan Eng (DAP-Bagan) said the inspector-general of police was "violating the supremacy of Parliament" by investigating Husni, as lawmakers have immunity in the House.

Lim said the speaker must make a ruling to stop the top cop from questioning Husni on the matter.

However, Ronald said the investigation was being done because there was a police report, and that he would not make a ruling to stop it.

"If there is a police report, the police have a responsibility to investigate.

"Parliamentary immunity is not absolute, it is subject to the Sedition Act," the deputy speaker added.

Chong Chien Jen (DAP-Bandar Kuching) pointed out that Husni's speech did not touch on seditious matters.

Ronald remained unmoved by repeated calls from Lim, as well as from his father Lim Kit Siang (DAP-Gelang Patah), for Parliament to protect the rights of MPs.

Husni is scheduled to be questioned by police at Bukit Aman this afternoon, on his speech made during the Budget 2017 debate last week.

He had questioned the purpose of 1MDB's existence and said repercussions from the 1MDB fallout could haunt Malaysia.

Former deputy prime minister Muhyiddin Yassin and former rural and regional development minister Shafie Apdal also spoke about 1MDB in the House last week.

The probe against Husni comes after speaker Pandikar Amin Mulia said the trio may have broken their oaths of secrecy.

Meanwhile after failing to secure a ruling, Guan Eng, Kit Siang and several DAP lawmakers walked out about half hour before the lunch break.

In the press conference that followed, Kit Siang shared how parliamentary immunity had spared him from a police probe.

"Police wanted to probe me over my speech. I told them there is a parliamentary privilege committee to investigate my speech because it will obstruct my duty as an MP (if they probe me).

"I told them to refer to their superior (who said they) will refer to the Attorney-General's Chambers and come back. They never came back," Kit Siang said.