Changes to Trade Me's privacy policy come into effect on December 9.

Trade Me's updated privacy policy appears to be a proposal for the unauthorised use of customer information, the Privacy Commissioner says.

Over the past few days Trade Me has been emailing customers who are opted out of its privacy option to inform them of changes to its privacy policy. From December 9, Trade Me would be able to collect their personal information to send them targeted advertising, the email said.

Users who are opted into the privacy option agree to Trade Me using their personal information, including cookie data and location, to send targeted advertising and disclose their information to trusted third parties using Trade Me.

Those who opted out in the past had not been sent relevant advertising because Trade Me hadn't been able to access personal information, the email said.

READ MORE:

* DATA FOR SALE: The value of our digital lives

* Apps tell Facebook intimate details, study finds

* Never-Googlers: Web users take the ultimate step to guard their data

* Facebook will pay users for data on the apps they're using

* Trade Me shareholders vote to approve $2.56b takeover offer

* Trade Me: The new investors calling the shots at an old Kiwi favourite

* Every New Zealander has about $1200 worth of unused stuff, Trade Me estimates

"It's often expected by our customers that we tailor our own marketing in this way, and we think it's reasonable too, so we're changing our policy to reflect this," it said.

Trade Me's privacy policy says information it collects includes among other things: details about customers' location information, IP address, hardware and software information, device information, device event information, and the pages, applications or services viewed or engaged with. It also tracks when customers used its services and their access times.

Privacy Commissioner John Edwards said he intended to seek further information from Trade Me on what appeared to be a proposal for the unauthorised use of customer information for marketing purposes.

"We will then evaluate the options available," Edwards said.

Under the Privacy Act those options were limited as there were no powers to sanction agencies for breaches of the information privacy principles, he said.

However, under changes proposed in the Privacy Bill before Parliament, the Commissioner would have the option to issue a compliance notice if a business practice of any agency appeared to be a breach of the act, he said.

Any customer concerned about the policy change should first raise contact Trade Me and, if they remained unhappy, should consider terminating their account, he said.

Customers wanting to make a complaint to the Privacy Commissioner would needed to show that the change had caused or was likely to cause them some loss or harm, or significant injury to their feelings, he said.

Trade Me spokesman Logan Mudge said it took its members' privacy seriously.

The change only impacted users who were opted out under its privacy options, he said.

"Nothing changes for the millions of Trade Me customers who are currently opted-in."

Anyone who chose to opt-out would not receive or see customised third party advertising on Trade Me, offsite customised advertising by Trade Me – for example Trade Me advertisements that were not on Trade Me's websites – have any information shared with businesses it had a stake in, or used in Trade Me's tailored products.

Andrew Hodgkinson, who has been a Trade Me user for about 10 years, said he had opted out of the privacy option in the past and was appalled at Trade Me's "extremely tone-deaf" decision to change its stance and start using all users' personal data.

"It just seems so out of touch and such a strange thing for them to do," Hodgkinson said.

He said he did not trust what Trade Me would use his personal data for.

"I have no way of knowing what exactly they are doing with that data," Hodgkinson said.

He said he would most likely delete his Trade Me account and use Facebook's marketplace instead because the US tech giant already had access to his data.

Other Trade Me users were quick to take to social media to express their concern at the privacy policy changes.

In May Trade Me was bought for $2.56 billion by British private equity firm Apax Partners.