An SLFP Spokesman said that the Election Commission and the Parliament’s Secretary-General will be informed of this decision in writing this week.
MPs Perera, Abeywardena, and Dissanayake had joined the Sri Lanka Podujana Peramuna (SLPP) party, while Soysa had supported presidential candidate Sajith Premadasa at the parliamentary poll.
The SLFP backed SLPP candidate Gotabaya Rajapaksa at the presidential election.
Meanwhile, the SLFP has appointed a five-member nomination board led by Professor Rohana Lakshman Piyadasa to chose the party's candidates for the parliamentary election.
Among those in the nomination board are SLFP General Secretary Dayasiri Jayasekara, and Mahinda Amaraweera.