Amid criticism and threats to its border security operation, the federal government is boasting a reduction in the number of asylum seekers reaching Australian waters.

In his weekly Operation Sovereign Borders update on Friday, Immigration Minister Scott Morrison reported there had been no boat arrivals in the past 36 days – the longest period without a maritime asylum seeker arrival since March 2009.

“The Australian government will continue to work with any and all partners, especially within our region to defeat the people smugglers and to continue to keep them informed of our own efforts and activities,” said a statement from Mr Morrison’s office.

But the government faces continued pressure about the lack of public information it is providing about its border security operation, with a refugee advocacy group questioning the Immigration Department’s right to hide behind public interest immunity.

The Refugee Advice and Casework Service told a Senate committee the government’s fear that the release of information would damage national security was overstated.

Labor leader Bill Shorten also took a swipe at the government for breaking a pre-election promise to report back to the Australian people about border security operations.

“On August 9, (Prime Minister) Tony Abbott said `if it’s a good week with boats, if it’s a bad week with boats, if it’s an in-between week with boats, we’ll be honest and open with the Australian people’,” Mr Shorten said.

“It is crazy that Australians can find out more about what is happening with our boats policy from the Indonesian press than they can from their own government.”

At sea, Indonesia has stepped up its naval presence monitoring its southern border after Mr Morrison admitted Australian vessels strayed into its northern neighbour’s territory.

“It’s not meant to be an unfriendly act to anyone,” Indonesian Foreign Minister Marty Natalegawa said of the move, which comes in response to news of the Australian navy incursion.

Meanwhile, Australia is scrambling to secure its aerial border patrols of the region as coastal erosion threatens an aviation fuel depot on the Cocos Islands.

Sandbagging is under way to keep tides at bay which could otherwise render useless by mid-2014 six fuel tanks which supply the Australian aircraft.