Consequently, Sensex settled 330.13 points lower at 40,323.61 while the broader Nifty lost 106.35 points to end at 11,905.70. This was Nifty's steepest fall in almost a month after showing recovery from lower levels in the last few sessions.
At noon, markets appeared to have taken the downgrade in their stride briefly as Sensex scaled a fresh high of 40,749.33. But poor earning numbers by state-owned GAIL, Bharat Forge and Allahabad Bank along with Moody's downgrade hurt the momentum.
"Rating downgrade forced investors to book profit in a volatile market and rupee weakened to a 3 week low. Given the subdued performance of the equity market during the year MF inflows fell to four month low while premium valuation of large & blue-chips is not attracting new funds in the market," said Vinod Nair, Head of Research, Geojit Financial Services.
The government in response to the rating downgrade said India continues to be among the fastest growing major economies in the world, and that the country's relative standing remained unaffected.
There were only six gainers during Friday's volatile trade session. Yes Bank settled 4.66 per cent higher followed by IndusInd Bank which jumped 2.98 per cent. ICICI Bank, Kotak Mahindra Bank, Tech Mahindra and HCL Tech gained up to 2 per cent.
The top losers were Sun Pharma, Vedanta, ONGC, TCS and Hindustan Uniliver which ended lower in the range of 2-5 per cent.
Deepak Jasani of HDFC Securities said there is a possibility of further weakness in the Nifty in the coming sessions. Jasani said that technically, Nifty falling sharply from near the new swing high of 12,034 levels could indicate a reversal pattern at the highs.
( With inputs from IANS )