Senior leaders of the platform took the decision at a meeting at Bikolpo Dhara Bangladesh secretary general Abdul Mannan's Gulshan house on Tuesday night.
After the meeting, B Chowdhury told reporters that they decided to hold a public rally at Suhrawardy Udyan in the third week of the current month.
He said they elaborately discussed various issues, including intensifying the activities of their alliance.
B Chowdhury, also the president of Bikolpo Dhara Bangladesh, said they gave Nagorik Oikya convener Mahmudur Rahman Manna the responsibility for holding talks with BNP to forge a unity.
Jatiya Samajtantrik Dal (Rob) president ASM Abdur Rob, Nagorik Oikya convener Mahmudur Rahman Manna, JSD general secretary Abdul Malek Ratan and BDB joint general secretary Mahi B Chowdhury were, among others, present at the meeting.