Australia's competition watchdog on Tuesday said it had no objection to Google's 3.1 billion US dollar purchase of online advertising firm DoubleClick.

In a decision that Google described as a world first among anti-trust regulators, the Australian Competition and Consumer Commission (ACCC) said it had no competition concerns about the deal.

"In this context, the ACCC considered that the merger was unlikely to result in a substantial lessening of competition in an Australian market," the ACCC said in a statement.

In a practice common in the industry, DoubleClick installs software bits referred to as "cookies" on Internet users' computers to track where they go online and what pages they view.  

Privacy advocates have expressed fears about the implications of Google and DoubleClick merging their expansive databases regarding people's Internet activities.

The ACCC is taking separate legal action against Google alleging the Internet giant mislead web users and misidentified sponsored links.