On coming to power, INC named her the Central Railway Minister. For the parliamentary elections 2009, she joined hands with the Indian National Congress-led United Progressive Alliance (UPA).She returned to the NDA in January 2004 and was named the Coals and Mines Minister of India until the dissolution of Lok Sabha in May 2004.In 2001, she ended her ties with the NDA and went on to join hands with Congress Party for the then West Bengal Assembly elections.After there was a hung assembly in the Centre in 1999 elections, she joined the BJP led National Democratic Alliance (NDA) as an ally and was given the charge of Railway Ministry.Mamata then left the Congress Party in 1997 and established All India Trinamool Congress the exact same year.She was discharged of her portfolios in 1993. She was made the Union Minister of State for Human Resources Development, Youth Affairs and Sports, and Women and Child Development in 1991.
Mamata was again elected as a Lok Sabha MP from Dakshin Bengal in 1991 general elections and kept on winning the seat in 1996, 1998, 1999, 2004, and 2009 elections.Due to the anti-incumbency, Mamata lost her seat in 1989 Lok Sabha elections.
She also served as the General Secretary of Indian Youth Congress.After defeating veteran Communist politician Somnath Chatterjee from the Jadavpur parliamentary Constituency in West Bengal in 1984 general elections, she became one of the youngest parliamentarians ever.Mamata served as the General Secretary of state "Mahila Morcha" of the Congress party from 1976 to 1980.She became a member of Indian National Congress in 1970.