Mitra resigned from his Lok Sabha seat Jan 15, accusing the Trinamool leadership of failing to keep its pre-poll promises after coming to power in the state.
A onetime arch-enemy of Mamata Banerjee when both were in the Congress, Mitra is regarded as the prime reason for Banerjee's decision to leave the Congress and float another party in 1997.
Later, the arch-rivals turned friends when Mitra joined the Trinamool in 2008 and a year later got elected as an MP on a party ticket from Diamond Harbour in the South 24 Parganas district.
