"We had invited the king as the head of state to officially open the event but we received communication that he won't attend," said Khangezile Dlamini, secretary of the Council of Churches.
"But that does not mean we won't continue," Dlamini told AFP.
The "national convention" was opening on Friday with the main talks due on Saturday, aiming to map out a direction on how Africa's last absolute monarchy can begin negotiations towards democracy.
Dlamini said Swaziland needed a transition to democracy and therefore civic society groups had taken the initiative to give government a blueprint of how the country could achieve multi-party democracy.
"We see this as an opportunity for civic groups to meet and draw out a road map on how the country could begin the process of political negotiations," she said.
Political parties in Swaziland have been banned since 1973 and recently activists have been jailed and harassed by police.
Mswati faces growing dissent over his authoritarian rule and is blamed for the crumbling economy, as a deepening financial crisis has left his government unable to pay its bills.
Pro-democracy groups, Aids activists and labour unions have staged unprecedented protests across the impoverished kingdom since April, complaining about the economic meltdown which is threatening the livelihood of the 1.2 million population.
The country is seeking a bailout from neighbouring South Africa, after failing to secure loans from international lenders, which have insisted on reforms before granting loans.
Swaziland Federation of Labour secretary Vincent Ncongwane said unions will attend the convention to show their commitment to dialogue.
"Yes, we are attending. We don't want the regime to use our refusal to attend the convention as an excuse to seek the much needed bail-out, arguing that we don't want to talk," Ncongwane said.