He continued with the same ministry after the 2004 elections which was won by the Congress led alliance, which included the DMK. His tenure as an Environment ministry came under intense scrutiny in 2011 during the 2G Spectrum case.
His association with the key accused in the 2G case, Unitech and DB Realty, was rooted to 2004 when he was the Environment minister. One of the key points out of the CBI is the approval of 2016 clearances given by his ministry in a span of two years from 2006 to 2008, some of which were associated with the trading of hazardous waste.