The deputy president of the opposition Democratic Party, Yukio Edano, appears to be forming a new party.
The move comes after party President Seiji Maehara last week said his party will not field any candidates for the coming election in late October.
Maehara said it would instead allow its members to run under the banner of a party recently founded by Tokyo Governor Yuriko Koike. Maehara said his party must take whatever means necessary to force the Abe administration from power.
Some Democratic Party members have been against the move after Koike revealed that she would only accept Democrats who agree with her views on national security, the Constitution and other major issues, which differ from the Democrats'.
Koike's party, "Hope," is in the process of deciding which candidates to endorse.
Against this backdrop, Edano said it is necessary to form a group for those who support the principles of the Democratic Party.
He will meet reporters later on Monday.