Transport and Civil Aviation Minister Arjuna Ranatunga said a large number of SLFP activists were ready to join the New Democratic Front election campaign.
Ranatunga's remarks came ahead of the signing of the agreement between the UNP and former President Chandrika Bandaranaike Kumaratunga.
Ranatunga added that the majority of SLFP MPs were not in agreement with the party's decision to support SLPP candidate Gotabhaya Rajapaksa.
Meanwhile, speculation was rife that a senior figure within the SLPP might align himself with Sajith Premadasa and the NDF. Commenting on the matter, a senior UNP figure said the crossovers would happen "at the right time".
However, no high-profile crossover has happened during the Presidential election campaign thus far.