Tamil Nadu Chief Minister J. Jayalalithaa Tuesday urged Prime Minister Manmohan Singh to advise Karanataka not to build any hydel power projects on the Cauvery.

She also requested the prime minister to tell the ministry of environment and forests not to give clearance to any project of Karnataka.

In a letter to Manmohan Singh released to the media here, Jayalalithaa said: "I seek your immediate intervention in the matter and request you to advise Karnataka not to take up any schemes including hydro electric projects in the Cauvery basin without the prior consent of the government of Tamil Nadu.

"I also request you to advise the ministry of environment and forests not to accord clearance to any project of Karnataka in the Cauvery till a permanent monitoring mechanism (Cauvery Management Board) is formed."

Referring to reports that Karnataka planned to build three reservoirs across Cauvery to set up a hydel power project at Mekedatu, she said the projects were new not contemplated in the final order of the Cauvery Water Disputes Tribunal.

"Further, the Cauvery Water Disputes Tribunal prescribes the total quantity of water to be used for consumptive use," she said.

She said Karnataka's plan was wholly illegal and was causing great distress in Tamil Nadu as it would hit the flow of the river considerably and severely affect irrigation in the state.