"Australia wide there were 14.0 million petrol powered vehicles registered in 2015 accounting for 77.7% of the total vehicle fleet.
In comparison there were 3.6 million diesel powered vehicles accounting for 19.7% of the fleet.
Over the five year period from 2010, the number of Passenger vehicles and Light Commercial vehicles registered with diesel fuel increased by 96.4% and 62.9% respectively."
Source:
http://www.abs.gov.au/AUSSTATS/abs@....5?OpenDocument
I downloaded the Excel document with more specific statistics (say that 10 times fast!); among passenger vehicles only, diesels account for 11.1% of registrations in Australia (all, not just new).
In Europe, as of 2011 (the most recent year available on the ACEA's website), diesels account for 36.8% of the vehicle fleet, and more than 50% of new passenger car registrations each year are diesels.