Four key activist groups on Wednesday accused Syria's main opposition National Coalition of failing to represent the views of the grassroots, in a sign that the anti-regime bloc was ever more alienated from the ground.
The groups demanded representation in the Coalition, and said they will not recognise any political group that fails to take their views into account.
The National Coalition has been meeting in Istanbul for over a week, and top on its agenda was a debate on whether it should join a US-Russia-led peace initiative on ending the civil war.
But bickering over the make up of the Coalition has stalled any progress.
On Wednesday, the four grassroots groups -- all of which were instrumental in organising protests against President Bashar al-Assad since early in the revolt that began in March 2011 -- issued a scathing statement against the Coalition.
"There is no doubt that the (Coalition's) leadership has failed to fulfil its responsibility to represent the great Syrian people's revolution at the organisational, political, and humanitarian levels," the activist groups charged.
"Any new (Coalition) members must represent our revolutionaries politically, and empower them by participating fully in the (Coalition's) decision-making process," they said.
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They also warned that they "will no longer bestow legitimacy upon any political body that subverts the revolution or fails to take into account the sacrifices of the Syrian people".
The statement was signed by the Local Coordination Committees, the Syrian Revolution General Commission, the Syrian Revolution Coordinators' Union and the Supreme Council for the Leadership of the Syrian Revolution.
The Coalition began meeting a week ago with four agenda items on its plate, chief among them a conference proposed by the United States and Russia on bringing rebels and representatives of Assad's regime to the negotiating table.
It must also choose a new president to replace Ahmad Moaz al-Khatib and vote on a new rebel government.
The group has yet to make a decision on any of the issues at stake.
Coalition dissidents have accused regional and Western powers of trying to impose their own agendas on the main anti-Assad political body.
More than 90,000 people have died in the country's war pitting troops against insurgents. The conflict broke out after the regime unleashed a brutal crackdown against dissent.