The proposed non-convertible debenture (NCD) programme of Tata Chemicals has also been rated `AA' while the rating agency has retained the `P1+' rating assigned to the company's Rs two billion commercial paper programme.

The revision in ratings was based on the negative outlook in the soda ash business on account of changed business fundamentals that has impacted the company's market position leading to increased pressure on margins and consequently, on the company's financial risk profile, Crisil said.

The rating also factors in the vulnerability of the fertiliser business to government policies as exemplified in the delays of several years in fixation of the retention price and the low likelihood of favourable resolution of issues in thenear term, it said in a release here today.

Meanwhile, the agency also revised downwards the rating assigned to steel manufacturer, Mukand Ltd from `BBB+' to `BB' on account of continued deterioration in financial risk with the expected losses in 1998-99 and further worsening in capital structure.

The rating also factors in the continued pressure on steel and non-steel business due to slack off-take and delays in full completion of the Hospet Steel Project.