The European Union this week is expected to smack Google with a third antitrust fine related to its AdSense advertising service, although the sanction will likely be smaller than the previous fines.

The investigation, which was opened in 2016, determined Google prevented third parties that use the AdSense product from displaying search advertisements from Google's competitors.  The EU believes that Google - which held 80 percent of the European market for search advertising intermediation over the previous ten years - had kept its anti-competitive practices for a decade.

Google responded by changing its deal with third parties to allow more leeway to display competing search ads.

Last year, The EU slapped Google with a record 4.34 Billion Euro (almost AU$7 Billion) a record 4.34 Billion Euro fine for using its popular Android mobile operating system to block rivals.  And in the year before that, the fine was 2.4 Billion Euros (AU$3.8 Billion) for blocking rivals of shopping comparison websites.