Five senior government staffers face possible arrest in a dramatic escalation of a probe examining officials’ knowledge about an explosive-laden caravan found on Sydney’s outskirts.

The high-ranking staff in the offices of NSW Premier Chris Minns and Police Minister Yasmin Catley failed to appear as summonsed on Friday at an upper house inquiry.

Committee chair independent MP Rod Roberts conducted a roll call for the premier’s chief of staff, James Cullen, and four other staffers on Friday before the committee set in motion a process to seek arrest warrants.

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In a letter to the committee announcing their intention not to appear, the staffers say appearing before the inquiry “would be at odds with the principles of ministerial accountability”.

Roberts pressed against that motion on Friday as he addressed empty chairs.

“The committee is not seeking to sanction ministerial staff for their actions, only to shed light on the events in the lead up to the passage of the hate speech and protest laws through parliament,” Roberts said.

Protest legislation

Controversial protest legislation was rushed through the NSW parliament in February after explosives, anti-Semitic messaging and a list of addresses of Jewish people and institutions were found inside the caravan at Dural in Sydney’s northwest on January 19.

The discovery prompted fears of a terrorist attack or mass-casualty event, as the premier and Prime Minister Anthony Albanese immediately dubbed it.

It later emerged to be a hoax, with senior NSW police telling Roberts’ inquiry they believed virtually from the outset it was a ruse.

The premier on Thursday attacked the upper house for “on a routine basis” trying to get government staff to appear at inquiries “almost like they’re criminals and under investigation, or they should front some kind of Star Chamber inquiry”.

“And if not, they’re under threat of arrest,” he said.

As members of the lower house, Minns and Catley cannot be compelled to appear at the upper house inquiry to give evidence.

Staffers, however, can be forced to appear.

The committee believes they were present during police briefings to the ministers.

Another staffer named in the motion, Minns’ deputy chief of staff, Edward Ovadia, said in the letter he should be excused from attending the committee as he was on leave at the time and did not attend any meetings.

The committee will ask the upper house president, independent Ben Franklin, to go to the NSW Supreme Court and seek warrants for their arrest.

The premier and police minister say they have commented extensively on the matter, including parliamentary hearings, press conferences and question time.