The shares were last quoting at Rs 64.50, down 1 per cent on the National Stock Exchange.
"...lowered foreign currency issuer credit rating on India-based IDBI Bank to 'BB+/B' from 'BBB-/A-3'. The outlook on the long-term rating is negative," S&P said in a release.
Standard & Poor's Ratings Services bases its rating on IDBI on the bank's 'adequate' business position, 'moderate' capital and earnings,'moderate risk position, 'average' funding, and 'adequate' liquidity, it said.
"We downgraded IDBI because we expect the bank's asset quality to remain weak over the next 12-18 months," said Standard & Poor's credit analyst Amit Pandey.
With inputs from PTI and Dion Global Solutions Ltd