Mizoram's former agriculture minister KS Thanga, who quit the Congress in June, joined the Zoram People's Movement (ZPM).
Thanga joined the ZPM at a programme at the Vanapa Hall in Aizawl on Thursday.
He had resigned from the Congress on June 9. He was a member of the state Congress's Political Affairs Committee (PAC), which was recently dissolved.
In his resignation letter, Thanga noted seven reasons for his resignation. He alleged that Congress state president Lalsawta was not following the party's constitution and acting on his own.
Thanga joined the Congress in 1994 and was elected MLA for two consecutive terms from the Aizawl South - III seat since 2008.
He was a parliamentary secretary for eight years before being made a minister in the then Congress government.