In the modern welfare state, austerity measures are what the government does when it basically runs out of money. Of course it's not limited to welfare spending, austerity-based cuts could be made in anything the government used to spend money on. (Then again, some people claim that anything the government spends money on is welfare.)
This is the key thing to do when you control the government: borrow as much as you can from the bankers, doesn't really matter what the terms are, as long as it's not so outrageous that your countrymen kick you out.
Then spend that money in whatever way you want, preferably in ways that favor the rich, such as union busting, undermining labor movements around the world, making the world safe for "pro-business" (ie. pro-exploitation) governments, bailing out institutions of the rich.
Finally, now that all the money is spent, get the poor in your country to pay back the money, with a hefty interest, to the rich who control the banks. And if they can't pay? Well, slash all social programs. Say austerity measures are all we can do at this point. Make the unemployed beg to be exploited.