Department backs border protection regime

Australia's "fearsome" reputation for border protection has been credited with stopping people smugglers, but any relaxation of the tough policy would see boats pour in, an inquiry has heard.

Home Affairs secretary Michael Pezzullo said Operation Sovereign Borders commander Air Vice-Marshall Stephen Osborne had correctly pointed out people smugglers were looking for chinks in Australia's defences.

"Should there be any opening, Air Vice-Marshall Osborne's assessment is absolutely correct - boats would pour in through that opening," Mr Pezzullo told Senate estimates on Friday.

He said Australia's fearsome reputation acted as a deterrent, which had allowed the government to move to a more flexible funding model.

"The way to Australia is currently closed," Mr Pezzullo said.

Australian Federal Police officers were careful to point out the reduction in full-time staff in Asia targeting illegal immigration wasn't due to a funding cut.

There are now four AFP officers spread across Sri Lanka, Indonesia, Thailand and Malaysia working on the issue, with other "surge" staff used.

The AFP insists the changes were a response to what is currently needed to combat people smuggling in the region.