Google is tracking you right into a store, even if you aren't using its Maps app.

The US$1 trillion ($1.4t) tech behemoth gloats of its cyberstalking capability in a blog post promoting its "Store Visits" marketing measurement service in which it claims "99 per cent accuracy" in telling if a person went into any of 200 million physical shops after seeing an online ad.

"Only Google can deliver this level of precision and scale," Google says in the Inside Adwords blog.

It does so by cross-checking anonymised location and clicking data from "hundreds of millions" of Google users.

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While a user must opt-in to sharing their location history, Google encourages this in the set-up of many applications, for example by saying that doing so will create a useful "private map".

However, the information is then used to feed the Store Visits machine for marketers.

University of Sydney media and communications department chair Tim Dwyer said the typical consumer wouldn't realise the extent to which their personal information was being traded away.

"The risks of 'surveillance capitalism' are not only the front-page scandals that we are seeing in mass data breaches like Cambridge Analytica, but they also result from the constant flow of information that is the product of the datafication of all our daily activities by simply using our devices," Associate Professor Dwyer said.

Questions about Google's Store Visits service are also raised in a presentation that data experts from Oracle have shown to the Australian Competition and Consumer Commission, which is investigating the "impact of information asymmetry" between Google and advertisers on one hand and consumers on the other.

The Oracle experts say Google collects masses of additional location data from phones that don't even have web services or apps open. The data is transmitted even if there's no SIM card, sent via little-known "activity logs".

Google calls these logs "location services", which is different to location history and opt-out, not opt-in. It says location services data is not shared outside Google.

Oracle says activity logs chew up on average one gigabyte of a user's mobile plan data each month.

A Telstra spokesman said it had asked Google to advise whether Oracle's claims are accurate.

Google dismisses Oracle's figures without providing any of its own.

It says Oracle has an axe to grind because the two are locked in a heated, multibillion-dollar legal battle in the US.

On Friday, News Corp Australia asked the Office of the Australian Information Commissioner's spokeswoman to confirm it had seen the Oracle presentation and what it had made of it. The OAIC did not provide any response.

Then yesterday in a statement on its website the OAIC said it had met with Oracle. It was now "making inquiries with Google and ... working closely with the ACCC on this issue".

Australian Communications Consumer Action Network CEO Teresa Corbin said: "Google should report on all data collected from consumers and ask for permission before any data is forwarded to third parties."