Regional chapter representatives of the Social Democratic Party confirmed in Tokyo on Friday the party's decision not to merge with the Democratic Party of Japan.
On Thursday, Takako Doi said she would step down as party president.
SDP Secretary General Mizuho Fukushima has emerged as a candidate to succeed Doi, although this issues was not raised at the meeting, attendants said.
Fukushima, 47, a former lawyer and well-known activist for women's rights, has long been considered a possible successor to Doi.
A new party president is expected to be elected Saturday in a meeting of SDP lawmakers. That decision will be formally approved at a party convention in December, according to party members.
The SDP suffered a crushing defeat in the general election on Sunday, leaving it with only six members in the House of Representatives. Observers had speculated that the SDP might disband and merge with the DPJ. The party had 18 seats when the Lower House was dissolved in October.
But attendants of Friday's meeting decided against disbanding, pointing out that the party had won 3 million proportional representation votes in the election.
Doi stepped down to take responsibility for the party's dismal performance in the general election.