The Gold Coast council will use a new city wifi service to harvest Facebook data from visitors to next month’s Commonwealth Games.

The data mining, which the council says is legal and will be used to help the city market itself to tourists, relies on visitors using their Facebook accounts to log into a new high-speed wifi service.

Users who object to sharing their Facebook data – amid growing concern about how personal information is obtained and used by companies and governments – can still access the free wifi, but the speed will be much slower and downloads restricted.

The city switched on the wifi service in the tourist hubs of Surfers Paradise, Southport and Broadbeach on Tuesday, 15 days ahead of the Games opening ceremony. It spent $5m to build its own infrastructure for the Games due to concerns about the speed and rollout of the national broadband network.

A city spokeswoman insisted the council would only make “limited use” of the data it mined from tourists. She insisted data would not be shared with “other agencies” although reports about tourist activity based on the information could be made available to the tourism sector “and other sectors as appropriate”.

“The most important information is about country of origin, to better understand the use by overseas tourists, who are one of the primary target groups for the service,” the spokeswoman said.

“The city will be able to understand patterns of demand and use, including how many people are accessing the service, times of day and the amounts of data used. It will also be very useful for understanding numbers during events and seasonal effects.”

The council said the data would be accessed by only “ a small number of city officials”.

“It should be stated that the city takes very seriously the protection of users’ data and information. The city will not be carrying out retrospective analysis of people’s Facebook accounts.”

The chair of the Australian privacy foundation, David Vaile, said anyone seeking to collect data should ethically require the “informed consent” of participants. That meant being upfront about the extent of the data collected, and to ensure people were aware before they logged on.

“The council has a very high obligation to be transparent. [A full list of data accessed] should be in an information document so people who want to maintain their privacy can choose to opt out,” he said.

In many cases, he said, people are asked to simply “click a button” with little information provided about the consequences.

Vaile said the council was effectively punishing people who wanted to protect their privacy, by allowing them access to the wifi service at a slower speed.

With the Games set to begin in two weeks, organisers and the tourism operators are scrambling to fill stadium seats and hotel rooms.

There are about 200,000 tickets still available – roughly one in six seats. Tickets can still be purchased to the sold-out opening ceremony through an official resale site.

The Games chairman, Peter Beattie, told reporters on Tuesday he was urging fans to help pack out venues for “the biggest event in Australia for a decade”.

“There’s still accommodation left, we’ve sold about 70%, so there’s plenty of rooms, plenty of airfares, plenty of tickets.”

Tourism operators are understood to be concerned that the city is not already at capacity for the Games.

The director of corporate affairs and strategy for the Gold Coast tourism bureau, Dean Gould, told News Corp some hoteliers had “sat on rooms hoping to get El Dorado sort of prices”.