Mumbai: After the inclusion of the Corus Group on Tata Group''s balance sheet, global credit rating agency Moody''s has downgraded Tata Steel Ltd''s corporate family rating from investment to speculative.

The agency gave a rating of ''Ba1'', against ''Baa2'' earlier, but kept the outlook for the company as stable.

Moody''s warned that rating may be downgraded further if Tata Steel experiences delays or cost-over-runs in execution of various expansion projects, fall in steel prices or failure in integrating the two businesses and realising synergies.

Moody''s said it expects Tata Steel''s ambitious capacity expansion plan to lead to higher project execution risk over several years and materially elevate financial leverage, but added that current high leverage limits the company''s financial strength and flexibility.

Earlier, Fitch Ratings had assigned a long-term foreign currency issuer default rating of ''BBB-'' to Tata Steel Ltd with a stable outlook.