Former Australian Treasury official and co-founder of Access Economics, Geoff Carmody, has written a great reposte to those whom oppose raising/broadening the GST because it is ‘regressive’. From The AFR:
… a flat tax on consumption, like the ideal GST, is regressive. But offering GST exemptions (fresh food), or a lower GST rate, means giving much larger absolute dollar concessions to the rich rather than the poor. The budget cost of such concessions overwhelmingly favours people who aren’t poor. This is wasteful and ineffective redistributive policy…