"What we do in our party is none of his (Modi's) concern," he told reporters on the sidelines of the 18th Convocation of National Institute of Mental Health and Neuro Sciences here.
Modi, at BJP's rally in Kolkata, had blamed the Gandhi family for twice denying the opportunity to Mukherjee to be the country's Prime Minister and urged people of Bengal not to forget this.
"This is democracy. Every political party has the right to form a group and individuals join any other party. I can't say anything about the Third Front," he said.
Signalling emergence of a third front, eleven non-Congress and non-BJP parties today formally joined hands as a block in Parliament to pitch for pro-people, anti-communal and federal agenda.