Mahinda made the proposal at a meeting of the JO last week, but Nanayakkara made a speech lasting around one hour giving his reasons against it.
Nanayakkara said the SLFP and the leftists had a responsibility to attack prime minister Ranil Wickremesinghe and his UNP.
Targeting the president will gain nothing, and it will only worsen a division of the SLFP and disappoint the supporters in the party, he said.
A careful political decision needs to be taken, instead of showing opposition on mere personal differences, he stressed.
According to him, the JVP has struck a deal with the UNP, but is opposing that party publicly in order keep its own party intact.
Therefore, attacking the president will only convince the SLFP supporters that the Rajapaksas were having an agreement with Wickremesinghe, added Nanayakkara.
Already, there is an opinion that the Rajapaksas were aiding the UNP to divide the SLFP, he said
Other leaders of the JO have approved of his views.