Looks like an attack by Fruit Fly - the female burrows into the fruits and lays her eggs, which then hatch and eat their way out. The droplets on the exterior of the fruit are characteristic of such an attack, although sometimes they may just look like small dimples in the fruits. I can see something white on the left side of the cut fruit - not sure what that is. The other possibilities are Codling Moth, which does the same thing as Fruit Fly (burrows into the fruits) or Oriental Fruit Moth, but with the latter, you would also see wilting tips to the branches, or on the new leaves, and webbing where the larvae nest. Oriental fruit moth attacks new leaves and stems as well as the fruits, and the management regime is somewhat different than for either Codling moth or Fruit fly.
Remove and dispose of any affected fruits as soon as you notice them. Once the fruitlets start forming, you can mesh the tree with material which has holes not more than 2mm, which will stop the Fly from accessing the fruits, though any such mesh will also reduce slightly the amount of sun reaching the fruits. There are pheremone traps you can buy and erect in the tree yearly, but they tend to only trap the males, and many other insects, and aren't very effective in orchards. They do, though, tell you if there are Fruit flies about. There will be chemical treatment sprays available, but I'm unable to recommend any because the pesticides you have in Australia will not be the same as those in the UK, therefore a trip to your garden supplies retailer for recommended chemical sprays would be useful. Depending on the treatments available, it may well be too late to treat this year's crop.
Note there are also pheremone traps for Codling moth which are quite effective for 1 or 2 peach trees, but again, not so useful in orchards, though pheremone traps should be erected in early spring, as flowering begins.