Labor’s deputy leader, Tanya Plibersek, has signalled she is open to giving intelligence agencies more tools to deal with a possible increase in domestic security threats from Australians being radicalised in the Syrian conflict.

Plibersek on Sunday gave a strong signal she was comfortable with telecommunications companies collecting and storing intercepted data for longer periods in order to assist intelligence agencies in their domestic anti-terror investigations.

The shadow foreign minister said the collection of metadata – the information we all generate whenever we use technology, from the date and time of a phone call to the location from which an email is sent – had aided the disruption of terror plots in Australia.

Plibersek played down the invasions of privacy posed by metadata sweeps, reasoning the intercepted material was the “envelope”, not the contents. “People describe it as keeping the haystack so you can go back and look for the needle afterwards,” she said.

She said metadata collections had been an important tool in safeguarding Australia’s national security. “We have disrupted some very serious terrorist plots in Australia,” Plibersek told Sky News on Sunday. “We’ve done it because we’ve got a strong intelligence community here. They do a good job.”

She was asked whether strengthening of the interceptions regime was justified in the wake of new threats posed by radicalised fighters returning from the Syrian conflict – an issue the Abbott government and intelligence agencies have expressed concern about.

“There continue to be threats. Those threats may increase,” Plibersek said. “I want to give (intelligence) agencies the maximum ability to do their job well, within the bounds that people would expect.”

Plibersek suggested she was comfortable in-principle with telecommunications companies collecting metadata and storing it for a mandatory retention period.

She said the community had a right to privacy, and to expectations of living in an open and democratic society – but her view was government needed to make it as “easy as we can” for intelligence agencies to protect against established and emerging threats.

The comments Sunday suggest Plibersek would be happy to revive a controversial plan shelved by the former Gillard government. That proposal would force Australian telecommunications companies, internet service providers and social media sites to collect metadata from Australian users and store it for two years.

Australia’s domestic intelligence agency, Asio, wants telecommunications data to be collected by companies and stored for two years – longer in some cases – for law enforcement agencies to access during their investigations.

A series of disclosures by the former National Security Agency contractor-turned-whistleblower Edward Snowden revealing the extent of coordinated online surveillance by the US, the UK and its allies, including Australia, have generated significant debate about whether governments are achieving the right balance between national security and privacy.

The Snowden disclosures prompted a significant rift in the Abbott government’s relationship with Indonesia (when it was revealed that Australia in 2009 attempted to tap the phone of the president and his inner circle); and also prompted the Greens and Labor to combine in the senate to establish a new inquiry into Australia’s telecommunications interception regime.

In submissions to that inquiry, the privacy commissioner and Australia’s intelligence watchdog, the Inspector General of Intelligence and Security, have flagged potential adjustments to the interception regime to ensure agencies strike the correct balance between protecting consumer privacy and conducting necessary investigations to prevent crimes.

Those agencies suggest more can be done to safeguard community privacy.

But while accepting the need for some adjustments, Asio has used the same inquiry to defend the central importance of a broad interception regime and the mandatory storage of private communications data for lengthy periods.

“Telecommunications interception of content is a key tool in preventing harm because people engaged in activities of security concern must communicate to progress their intentions,” Asio says in its submission to the senate.

“Access to telecommunications content provides essential details of activities of security concern and enables Asio to provide advice and take action to protect Australia,” it says.

“In terms of data retention periods required for Asio to effectively discharge its functions, at least two years is required in some cases, whether by carriers, carriage service providers, or ancillary service providers. Due to the nature of activity by clandestine foreign actors, retention for longer than two years would be ideal.”

The government has been signalling for months it is exploring steps to increase protections for Australians given the Syrian situation.