Activists allege contamination from abandoned factory, after world's worst industrial disaster in 1984, continues to affect people's health and environment.

Bhopal Group of Information and Action (BGIA) local NGO representative Rachna Dhingra said they received a response from Union ministry for environment, forests and climate change joint secretary Biswajit Sinha on April 8. "A four line message just stated our request for inviting UNEP for a study has been examined and they did not find a necessity for the study at present," she said.

"We are distraught with this information because Sinha doesn't even bother to share reasons for rejecting this offer," she added.

Earlier, Bhopal Group of Information and Action (BGIA) and its global supporters had roped in UNEP to undertake evaluation on spread of toxic waste.

"We were thrilled by UNEP proposal as it brought experience, expertise and UNEP being a third party will carry more credibility in Indian and in the US courts. It would strengthen government's case against Dow Chemicals," said Dhingra.

On February 19, when NGO representatives met Union minister Prakash Javadekar over the UNEP proposal he had asked for 15 days to deliberate on the offer. It called for UNEP assessment of 3.5 km area around the factory that continues to affect inhabitants in some 22 colonies.

"Minister's refusal to take UNEP assistance is only helping Dow Chemicals and delay in clean-up continues to adversely affect population," she added.

Experts agree that such clean-up can only begin after a comprehensive scientific assessment of the depth, spread and nature of contaminants is completed, she said.

Holding Dow Chemical liable for environmental damage in Bhopal, Union government filed an application in 2010 in Madhya Pradesh high court for Rs 350 crore as an advance for clean-up, but there has been no movement on this in last five years.

In 2001, Dow Chemical took over Union Carbide's global assets.