Kostis Hatzidakis, who is now an opposition MP, was left with blood pouring from his head after being chased and beaten by dozens of protesters.
He was set upon by up to 100 youths, who shouted "Thieves" and "Shame on you" when he emerged from the Greek parliament building on Constitution Square, in central Athens.
Protesters hurled lumps of concrete and paving stones at riot police, set fire to cars and smashed shop fronts.
The violence in Greece erupted during a general strike called by unions to protest against new labour laws which unions say will give employers too much power and take workers' rights "back to the Middle Ages."
Greece is struggling to reform its economy under conditions set by a 110 billion euro international bail-out package but many Greeks feel that they have ceded away their sovereignty to the European Union and International Monetary Fund.