Alleging that the prime minister under the UPA government was powerless, the Environment Minister also accused Congress President Sonia Gandhi of interfering in important decisions during her party's rule at the Centre.

"She (Natarajan) has mentioned certain files and she has not mentioned certain files but she indicated what was happening. But one thing is clear, that the Prime Minister (Manmohan Singh) was in office, but not in power.

Read more: As it happened: Jayanthi Natarajan quits Congress

"The power was concentrated in 10, Janpath (residence of Sonia Gandhi). So, we will definitely look into the cases mentioned and hinted at, where some extraneous influence has happened. We will see if there is any trace of such extraneous influence," the minister told reporters on the sidelines of a function here.

Natarajan had written to Sonia Gandhi alleging that she had received specific requests from her son and Congress Vice President Rahul Gandhi on environmental clearances and, consequently, had rejected big ticket projects.

Javadekar had earlier termed it a "serious issue" and said he would review the files regarding which allegations of extraneous influence have been made.

Read more: Javadekar says he will review files mentioned by Jayanthi

Natarajan had quit the party last week after launching a scathing attack on Rahul and Sonia Gandhi.

She had claimed she had followed the Congress Vice President's directions but he later "changed his stand in favour of corporates" and she was "vilified, humiliated and sidelined" by the Congress leadership.

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