The dialogue is intended to end a crisis sparked by the Islamist leader's decision to expand his powers.
Speaking in a televised address on Thursday night, Morsi had invited political leaders and others for talks on Saturday and said plans for a December 15 referendum on a new constitution were on track. This despite clashes that killed seven people.
"The National Salvation Front is not taking part in the dialogue, that is the official stance," Ahmed Said, one of the leading members of the coalition who also heads the liberal Free Egyptians Party, told Reuters.
Prominent reformist Mohamed ElBaradei and the Wafd party, both members of the liberal-minded coalition, said they would not be taking part.
"I appeal to all national forces not to participate in dialogue that lacks the basics of real dialogue, we are for dialogue that is not based on arm-twisting and imposing a fait accompli," ElBaradei said in a message on Twitter.
Morsi's administration insists the president's actions were aimed at speeding up the transition to democracy that had been hampered by a judiciary still packed with appointees of ousted president Hosni Mubarak.
An unfair dialgoue
The Front has demanded that Morsi scrap his decree that put his decisions beyond legal challenge and postpone the referendum.
Said said the Front had come out against talks because Morsi had said he would press ahead with a referendum regardless.
They also stated that he had prejudged the agenda by outlining parts of his decree that could be amended before talks had even begun.
"He has already set the ceiling of the discussion and has already made limits to it," Said stated.
Said also felt that the president was ignoring protests and violence on the street.
"Is this an environment for people to say 'yes' or 'no' to a document that is going to divide them rather than unite them?" he asked.
He added that voting abroad in the referendum was set to start on Saturday, meaning it had already been set in motion.
The foreign ministry announced the Saturday start to voting abroad on its official Facebook page.
Another member of the Front, Amr Moussa, also said the group was sticking to its demand that the referendum be delayed, amongst other demands. – Reuters