"Almost 90 percent of Tunisian voters ignored this piece of theatre and refused to be involved in the process," Ahmed Nejib Chebbi, head of the National Salvation Front, told journalists.
"I call on political groups and civil society to join hands to work for change, in the form of Kais Saied's departure and early presidential elections."
Following a similar turnout in December's first-round vote, Sunday's poor participation was another blow to Saied, who has stripped the legislature of its powers and granted himself far-reaching authority since his dramatic 2021 power grab in the birthplace of the Arab Spring uprisings.
On July 25, 2021, Saied sacked the government and froze parliament before dissolving it and pushing through a new constitution -- granting him almost unlimited powers and sweeping away the system that had emerged from the 2011 revolt.
The latest poll was seen as the final pillar of Saied's transformation of politics, ushering in a new legislature that will have almost no authority to hold the president or government to account.
The National Salvation Front, which includes the Islamist-inspired Ennahdha party, said the low turnout exposed "the total failure" of Saied's project, and said it would not recognise the new parliament.
Chebbi urged key bodies including the powerful UGTT trade union federation, which has hesitated to openly oppose the president, to join forces.
Speaking after voting ended at 6:00 pm (1700 GMT), electoral board chief Farouk Bouasker said 887,638 out of more than 7.8 million registered voters had taken part in the poll, which followed December's widely boycotted first round.