"The party of the Unbowed will only govern with the purpose of implementing its own program… I will not join a government that will neither restore fair taxation nor conduct a policy of fair wealth distribution," Manuel Bompard told the BFMTV broadcaster.
The centrists, who floundered in the first round of the snap parliamentary polls, have been considering forming a united front against the first-placed right-wing National Rally by working together with the runner-up leftist New Popular Front alliance, which includes France Unbowed.
French newspaper Le Monde estimated that at least 190 candidates from Ensemble and the New Popular Front had withdrawn from this Sunday's runoff in the hope of boosting the chances of stronger candidates defeating the National Rally.
Ensemble won 20.04% of the vote on Sunday. The National Rally and its allies won 33.15%, which translates into up to 270 seats in the 577-seat National Assembly, while the New Popular Front secured 27.99% of the vote. A party needs 289 seats to have an absolute majority.