The 30-share index, which ended 158.79 points lower in the previous session, fell by another 158.77 points, or 0.99 per cent, to 15,849.57 in opening trade.
In a similar fashion, the wide-based National Stock Exchange Nifty index declined by 50.30 points, or 1.01 per cent, to 4,754.80.
Stocks of consumer durables, metal, banking and refinery sectors remained under selling pressure, dragging the Sensex down.
Brokers said sustained selling by funds, triggered by stiff opposition to policy reform opening up the multi-brand retail sector to foreign direct investment and a weakening trend in Asian markets on renewed worries over the European debt crisis, mainly depressed the trading sentiment.
In the Asia region, Hong Kong's Hang Seng Index was trading 0.73 per cent lower, while Japan's Nikkei shed 0.83 per cent in morning trade today.