The environment ministry used to be the reason behind most project delays. This seems to have changed, according to a government study of over 1,000 projects.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/environment-ministrys-five-step-process-faster-clearance
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/economic-times-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/thesaurus/environment-clearance-ec
[4] http://admin.indiaenvironmentportal.org.in/thesaurus/forest-clearance
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/wildlife-clearance-0
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/eco-sensitive-zone
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/ministry-environment-and-forests-moef
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/forests
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/land