Prime Minister Manmohan Singh will not inaugurate Tamil Nadu government's ambitious Adyar Eco Park as scheduled during his visit here on Monday, as the union environment ministry has not given its clearance for the project.

"Since the union environment ministry has not given its clearance to the proposal sent by the Tamil Nadu coastal zone management authority, the Prime Minister will not inaugurate it as scheduled on January 3," the state government said in an official release here on Wednesday.