The ACCC is concerned Google could stymie access by Fitbit’s competitors such as Samsung, Garmin and Oppo to some Google services, as well as elements of Google's Android system that allow wearable tech devices to work effectively.

In December, the ACCC rejected a long term behavioural undertaking offered by Google that sought to address competition concerns because it said there would be significant difficulties in effectively monitoring and enforcing compliance with the undertaking.

The ACCC said it would continue to work closely with overseas agencies including the US Department of Justice (DOJ) which is also continuing its investigation into "whether Google’s acquisition of Fitbit may harm competition and consumers in the United States".

A Google spokesperson said the tech giant had voluntarily engaged with the ACCC since the deal was first announced in November last year and remained willing to continue engagement during the regulator's ongoing investigation.

"We're confident this deal is pro-competitive and will result in greater choices and benefits for consumers, both globally and in Australia," the spokesperson said. "We complied with the DOJ’s extensive review for the past 14 months, and the agreed upon waiting period expired without their objection. We continue to be in touch with them and we’re committed to answering any additional questions."

Fitbit's co-founder and chief executive James Park attempted to allay concerns about privacy and competition in a message sent to Fitbit's 29 million active users on Friday morning.

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"The trust of our users will continue to be paramount, and we will maintain strong data privacy and security protections, giving you control of your data and staying transparent about what we collect and why," Mr Park said. "Google will continue to protect Fitbit users’ privacy and has made a series of binding commitments with global regulators, confirming that Fitbit users’ health and wellness data won't be used for Google ads and this data will be kept separate from other Google ad data."