Tunisia's secular opposition, angered by two assassinations in its ranks and emboldened by the overthrow of Egypt's president, said on Sunday it was considering setting up an alternative "salvation government" to challenge the Islamist-led leadership.
If agreed, the move would mark a significant escalation by the country's opposition groups, who say they have no interest in reconciliation with the ruling Ennahda party.
"We will meet this evening to discuss creating a new salvation government and will study the possibility of nominating a new prime minister to replace this failed government," said Jilani Hammami, a leader of the Salvation Front coalition and Tunisian Workers' Party.
"There is no longer any doubt that the time for it to go has passed."
Tunisians are bracing for what many worry may be one of the most tumultuous and critical periods in their transition to democracy since the toppling of autocratic president Zein El Abidine Ben Ali in 2011, a revolt that inspired uprisings across the Arab world.
Last Thursday, assailants gunned down the opposition figure Mohamed Brahmi - the second assassination targeting the secular opposition in six months.
The opposition blames the Islamist Ennahda party for the killing and protests have erupted in the capital Tunis as well as other provincial cities.
The secular opposition had already been poised to mobilize against the Islamist-dominated government, inspired by the mass protests in Egypt that saw the army oust and detain the former Islamist president.
Critics of the Tunisian opposition say the campaign is threatening stability during a fragile transition process.
The speaker of parliament said on Saturday the government was discussing a new power-sharing deal and urged lawmakers withdrawing from the transitional Constituent Assembly to reconsider.
"It's not rational to throw in the towel just metres away from the finish line," Mustafa Ben Jaafar said in a televised speech.
Ben Jaafar, a member of one of the secular partners in the Ennahda-led government, said the body was only weeks away from finishing the new constitution.
But the opposition position has hardened.
"The opposition completely rejects all efforts at reconciliation presented by the head of the Constituent Assembly in terms of expanding powers," Hammami told Reuters.
By Sunday, the number of parliamentarians who had withdrawn from the 217-member body had risen to 64. The lawmakers will join a sit-in outside the parliament.
Protests started there on Saturday after Brahmi's funeral and drew crowds of thousands, the largest the capital has seen in months. Hundreds of pro-Ennahda demonstrators took part in a rival rally, signalling the possibility for the protests to descend into violence.
Police used teargas to disperse protests in Tunis as well as Sidi Bouzid, the birthplace of the Tunisian revolt and hometown of the slain Brahmi.