Matsumoto was elected to the House of Representatives for the first time in 1990 as a member of the Japan Socialist Party.

He followed in the steps of his grandfather Jiichirō Matsumoto and father in command of the Buraku Liberation League.

[1] Matsumoto resigned from the post of the Minister of Reconstruction and from the vice-chairmanship of the Buraku Liberation League after making harsh and abrasive criticism of the two governors from the area affected by the Great East Japan earthquake as well as threatening to ruin the career of any journalists who reported his remarks.

He later apologised and then blamed his behaviour on his Fukuoka background and also on his B-blood type, a popular superstition in Japan.

[2] Matsumoto's was criticised for his intimidation of journalists when he told them that "Your company is over if you publicize my remarks" as the essence of the liberation alliance.