IDBI Bank shares opened lower and lost a further 2 per cent to Rs 63.65 on the BSE. On the National Stock Exchange, the stock fell 2 per cent to Rs 63.50.
The foreign currency issuer credit rating on IDBI Bank was cut to 'BB+/B' from 'BBB-/A-3'. The outlook on the long-term rating is negative, S&P had said.
'BB+' is considered the highest speculative grade, while 'BBB-' reflects adequate capacity to meet financial commitments, but more subject to adverse economic conditions.
"We downgraded IDBI because we expect the bank's asset quality to remain weak over the next 12-18 months," S&P credit analyst Amit Pandey said.