Home Affairs officials have batted away questions relating to the caravan of explosives discovered in northern Sydney.
The vehicle was discovered at Dural in the city's north-west last month, containing industrial explosives and the names of Jewish sites.
A man named in connection to the caravan was charged over a separate anti-Semitic attack as police probe potential links between the incidents and organised crime gangs.
The blast material was found to be up to 40-years-old.
Opposition home affairs spokesman James Paterson grilled officials during a senate estimates hearing on Monday, about why they couldn't say if a report had come into the National Emergency Management Agency following the discovery of the caravan.
"That issue is subject to an ongoing New South Wales joint counter-terrorism team investigation, and we are not in a position to answer any questions about that incident while that inquiry is ongoing," an official responded.
After a line of questioning from Senator Paterson, Employment Minister Murray Watt retorted "a very good question to put the AFP".
When Senator Paterson hit back, Senator Watt accused the Liberal of "playing politics".
"It's rather disappointing that someone who aspires to be the home affairs minister of this country is seeking to have disclosed publicly details that are relevant to a police investigation," the Labor senator said.
Senator Paterson asked if the reason behind the lack of answers was because the government was "embarrassed".
Greens Senator David Shoebridge asked when home affairs was first made aware of a potential incident involving a caravan and explosives.
Department secretary Stephanie Foster took a number of questions on notice after a back and forth, as it was not in her "power to determine what information relating to this incident would be prejudicial to the inquiry".
With the federal election expected to be called in a matter of weeks, this round of estimates is set to be the last before the vote is held.
