With Prime Minister Tony Abbott and Attorney-General George Brandis pushing for two-year storage of all Australians' "metadata" so that law-enforcement agencies can access it to fight terrorism and crime, we take a look at the issues many academics, privacy advocates and civil libertarians have raised about the scheme.

What is metadata?

At present, there is no formal definition of metadata under Australian telecommunications law.

In the act that governs access to it – the Telecommunications (Interception and Access) Act 1979 – it is simply referred to as "telecommunications data", which it describes as everything but the "content" or "substance" of communications, that is, what was said on a call or over the internet.

"The [act] does not contain a specific, positive definition of metadata [referred to as 'telecommunications data']," the federal Parliamentary Library, which recently examined the act, said in its analysis.

Metadata usually includes phone numbers called or received when using a mobile phone or fixed-line telephone, the location from which the calls were made, and the duration of the calls. But when surfing the internet, the definition of what constitutes metadata gets a little bit murkier.

Communications Minister Malcolm Turnbull has said internet metadata stored under the government's plan will include the IP address assigned to your modem, as well as email addresses and timestamps of emails, but not an email's subject line or contents. No web browsing history will be stored, he has assured the public.

Why the government says data retention is needed

Australian intelligence and law-enforcement agencies say they are going "blind" when it comes to accessing call and internet records, because telephone and internet companies are deleting data they have previously stored for billing purposes.

Mr Abbott wants Labor's support to pass a data retention regime through parliament before March 26 that would require the records to be stored.

Recommendations from the Coalition-dominated Parliamentary Joint Committee on Intelligence and Security are to be released on Friday.

The committee's recommendations will either be accepted by the government or rejected before debate commences on the bill that will enforce mandatory data retention – the Telecommunications (Interception and Access) Amendment (Data Retention) Bill 2014.

A spokesman for Attorney-General George Brandis told Fairfax Media there was no set time or date for a response to the recommendations.

But using the first two tranches of national security legislation as a guide, it is not likely that a response will be made on the day the report is released.

Why should you care?

Metadata was disclosed more than 580,000 times in Australia in the past financial year to law-enforcement and intelligence agencies for fighting welfare fraud, and a whole host of other crimes.

Spy agency ASIO is not included in these reported figures because it is exempt from having to disclose the number of requests it makes.

The figure means a significant proportion of the Australian population is likely to have had its metadata accessed in some way.

Separately, it was recently revealed that 19 law-enforcement agencies in Britain made 608 applications for journalists' metadata during a three-year period.  This led to Britain rushing through guidelines to prevent police snooping on journalists unless they  obtained a court order.

The Australian Federal Police have refused multiple Fairfax requests to reveal how many journalists have been targeted in Australia, although it is known that veteran political reporter Laurie Oakes had his telephone records trawled in 2008 to find out who was behind a cabinet leak.

Journalists reporting on the federal government's asylum-seeker policies have also been repeatedly referred to the police in attempts to uncover confidential sources. This almost always leads to a journalist's call records being trawled to identify a source.

It's likely many other Australian journalists have been targeted and don't know it.

What are the complaints?

Besides concerns about freedom of the press, there is no judicial oversight to access the data – no judge signs off on a metadata search request. There is also the potential for an "internet tax" to be passed on to consumers because of the cost of setting up the regime.

The Prime Minister says the scheme will cost almost $400 million to set up. If the laws are passed, one of Australia's largest internet providers, iiNet Group, has said that if it were required to bear the costs of a data retention regime then customer internet bills could go up by $10 a month.

The government is understood to be considering a 50-50 cost-sharing arrangement with industry for upfront capital costs.

Other concerns are the length of time the data is stored and whether two years are appropriate, exactly what data is stored, the potential for misuse, the secure storage of the data and which agencies have access.

Who has access?

Of most of the complaints, the big one is who has access to the data. What many people don't realise is that, already, some Australian law-enforcement agencies are able to access your metadata if telcos such as Telstra and Optus retain it.

Agencies that can access metadata include federal, state and territory police, Medicare, Bankstown Council in NSW and other councils throughout Australia, Worksafe Victoria, the RSPCA, the Tax Office, Australia Post, domestic spy agency ASIO, financial regulator ASIC and many others when conducting criminal and financial investigations.

The government attempted to address this issue by limiting the number of agencies that have access by way of the data retention bill's regulations.

But this backfired, with civil liberties groups saying it would allow the regulation to be updated without parliament's approval by the attorney-general of the day, meaning any agency that wanted access that had been taken off the list of approved agencies can be put back on it by the attorney.

ASIC, which was taken off the list, has already said it will apply to the attorney to be put back on.

Potential for misuse

There are many uncontroversial reasons to access metadata including allowing police to solve crimes by, for example, using mobile phone data to pinpoint the location of a suspect.

However, some controversial requests have been uncovered. For example, Bankstown Council used metadata to find illegal dumpers and fine them.

Meanwhile, officials at Queensland Police began accessing the private metadata of cadets in August 2013 to determine whether they were sleeping with one another or faking sick days. This access was labelled by the state's police union as "disturbing" and "potentially unlawful".

Is there an international precedent for these laws?

In April, a similar data retention scheme in the European Union was ruled "invalid" by the Court of Justice in response to a case brought by Digital Rights Ireland against the Irish authorities and others.

Soon after, notwithstanding the ruling, Britain passed new "emergency" laws that made it mandatory again.