A Senate inquiry has been warned that relations between Australia and Indonesia could be damaged by the disclosure of documents related to asylum seeker boat interceptions.
Immigration Minister Scott Morrison and Operation Sovereign Borders commander Angus Campbell are giving evidence before an inquiry into government secrecy over border protection operations.
It is the first time a minister from parliament's lower house has fronted a Senate inquiry since 1992.
The Senate's legal and constitutional affairs committee is examining the government's public interest immunity claim to deny the upper house access to official documents.
Lieutenant-General Campbell warned the disclosure of certain documents could undermine international cooperation and agreements.
"The documents requested relate to operational matters that I believe should not be disclosed," he told a hearing of the inquiry in Canberra on Friday.
"These documents may impact upon Australia's relations with foreign states and damage those relationships."
Lieutenant-General Campbell also believed it was too early to provide more information on the 22 boat arrivals that took place in the early phase of the operation, which started on September 18.
Operation Sovereign Borders would not have achieved the objectives it had without a limit on the information it released publicly, he said.
"We would not be where we are today."
There have been no boat arrivals since December 19.
Greens senator Sarah Hanson-Young quizzed Customs boss Michael Pezzullo about what happened to asylum seekers who were in the department's custody at sea but not transferred to an immigration detention centre, presumably because their boat had been turned or towed back to Indonesian waters.
"Your question is an attempt to speak about operational matters covered by the public interest immunity," Mr Pezzullo said.
To discuss in detail operations conducted since December 19 invited him to potentially breach the public interest immunity claim, he said.
By way of implication it asked him to talk about how asylum seekers who had been intercepted, but not detained, had been handled.
"It's an indirect way to breach the claim of immunity and I'm not prepared to do that."
"We frankly don't give a damn about the media cycle and what's going to be said on morning radio and Q&A and the rest of it," he told the hearing.
Providing running commentary on operations and the location of assets gave away an advantage to people smugglers.
Mr Morrison clarified what information the government was prepared to provide.
Weekly updates detailed the number of asylum seekers transferred into detention, population numbers at offshore detention centres, the number of voluntary and involuntary returns and details of other incidents and arrests.
But disclosure of on-water tactics, training procedures, operational instructions, specific interest reports, intelligence, deployment of assets, timing of operations and passenger information would prejudice current and future operations.
Mr Morrison, when asked at what point authorities intercepted asylum-seeker boats, told the committee: "Where they're legally able to be done."
Labor senator Joe Ludwig said Operation Sovereign Borders lacked parliamentary scrutiny, allowing it to be more secretive that Australia's national security service, ASIO.
Earlier he told the inquiry the committee wanted to "throw light in dark corners" so there was no secrecy about the operation.
Senator Ludwig also argued that claims for public interest immunity could not be made in a general sense.
They had to relate to specific documents, individually not collectively.
In a testy exchange, Labor senator Kim Carr accused Mr Morrison of not reading the documents excluded for release before he made a claim of public interest immunity.
"I want a specific answer. Did you read the documents?" Senator Carr asked.
"I'm aware of the documents," Mr Morrison said repeatedly.
The inquiry hearing continues.