Right to Information activist Saket Gokhale Thursday joined the Trinamool Congress in New Delhi.
He said the Mamata Banerjee-led party takes an "aggressive" stand on issues.
"The TMC is the second largest Opposition party in Parliament and it has been my obvious choice. If you look at all the national parties, the TMC takes an aggressive stand. The way the chief minister of Bengal has been fighting on the front foot, that's what I'm looking for," Gokhale said after joining the party.