Environment Minister Jayanthi Natarajan has strongly opposed the government's decision to equip the National Investment Board's (NIB) with powers to clear big projects without seeking clearances from the environment ministry.

A per powers envisaged for the NIB, which has been proposed by Finance Minister P Chidambaram with a sole objective fast-track clearances for mega projects, a project once cleared by the body can't be stalled by any ministry.

In a letter written to Prime Minister Manmohan Singh, Natarajan opposed such powers for the NIB, saying the Board would undercut the powers of the environment ministry.

Natarajan wrote in the strongly-worded letter, "This concept is unacceptable. The NIB has no constitutional authority to decide on the failure of any minister."

She said the proposed changes would have all-embracing consequences on the way ministries operate. She asked who would answer in Parliament in case any decision of the environment ministry is overruled by the NIB.

Apart from the Environment Ministry, the Ministry for Tribal Affairs is also concerned over the finance minister's proposed NIB.

A Cabinet Note on the proposed NIB, which would be headed by the Union Finance Minister, has already been drafted and will be circulated among the ministers very soon.