"After meetings with many international delegations in recent weeks... the Syrian National Council (SNC) confirms it sees no reason to attend the Geneva conference," SNC member Samir Nashar told AFP by telephone.
Nashar also forecast that the National Coalition, which has still not taken a definitive decision, would similarly not show up.
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Friday's announcement reiterates a statement by SNC president George Sabra in October that the group had taken a "firm decision" not to attend the talks.
At the time, Sabra also said the National Council would withdraw from the National Coalition if it decided to attend.
The SNC, which is one of the most important members of the opposition, has long said it will not negotiate until President Bashar Assad's regime is toppled.
After months of delays, a January 22 date for the peace talks has been set, but doubts remain about whether the conference will go ahead.
The talks were originally scheduled to be held in the Swiss city of Geneva but have been moved to nearby Montreux.
Nashar said the decision was taken after many meetings with various authorities and organizations, including the "Friends of Syria" group of states that support the opposition, the UN-Arab League envoy Lakhdar Brahimi, and the Russian foreign ministry.
"The whole idea of Geneva is flawed. It is based on bridging the demands of the Syrian regime and the opposition, placing them on an equal footing. We reject this," said Nashar.
"There is nothing the international community has to offer that would make us revise our earlier decision."
The SNC has long held the view there should be no talks without guarantees they would lead to Assad's fall.
"And the message we are getting is that whether Assad stays or goes will be up to the Syrians to decide. The United States supports our demand that he must fall but the Russians do not accept this as a precondition," said Nashar.
Asked about how the decision might affect the Coalition's thinking, he said: "The Coalition will not end up going. Not only is the Council against participation, there are many other opponents within the Coalition who reject the talks and will vote against going."
The Coalition is set to hold its next general assembly meeting in Istanbul on Sunday and Monday.
"Also you have to look at what the revolutionaries on the ground are saying: they too reject Geneva," said Nashar.
"What this means is there will be no Geneva at all," he added.
Four Norwegian and Danish vessels, which are due to ship hundreds of tons of deadly chemicals out of Syria, headed for international waters off the Syrian coast on Friday, a Norwegian military spokesman said.
The ships left the Cypriot port of Limassol, about 160 miles west of Latakia port where they are due to collect their chemical cargo.
Once they have removed the chemicals from Latakia, the Nordic vessels will be escorted by Russian and Chinese ships to an Italian port where the cargo will be loaded onto a US-owned ship adapted to destroy the chemicals.
The US vessel, the Cape Ray, is due to leave the United States for the Mediterranean in about two weeks.
Reuters contributed to this report