The PPE is an economics flavored arts degree.
By default it only includes a third of the core economics courses (Micro 1 and 2) you could put Micro 3 and Macro 1, 2 and 3 in as electives if you wanted, but you won't get the same breadth within economics as you'd get from doing an Economics Degree.
Honestly if you want to be an economist study economics, get high marks, do extra curricular stuff, try and get relevant work experience and do honours.
By and large getting into federal government jobs doesn't depend too much on what degree you did. Places like Employment, Social Services, etc.
However for the really desirable analytical sort of jobs that are actually "economist" jobs, like in Treasury or the Reserve Bank you really want an honours degree in Economics as a minimum, and yeah if you want to be an economist in the private sector you ought to have an honours degree in Economics.
It'd probably be possible to do the PPE, get into an APS grad program and end up as a policy officer or something, then do a masters in development economics through the Crawford school and then go from there - but if you're already pretty much set on being an economist why bother? If you're set on economics and want a broader degree with History, Politics or Philosophy in it study Arts/Economics. Economics is easy to combine with something else and it's usually only one extra year.
