Thirty one lawmakers from Tunisia's ruling Nidaa Tounes party resigned from their parliamentary bloc on Monday, deepening a row over party succession.

The secularist Nidaa Tounes, elected to power last year in a vote hailed as a democratic victory after Tunisia's Arab Spring revolt, has been riven by months of infighting.

The deputies who resigned Monday, nearly a week after suspending their membership in the party's parliamentary bloc, are supporters of Nidaa Tounes secretary general Mohsen Marzouk.

Marzouk's supporters accuse President Beji Caid Essebsi's son Hafedh of trying to seize control of the party.

"We had to resign from the parliamentary bloc as a first step toward our defence of democracy and parliamentary credibility," one of them, Hajer Laaroussi, told reporters.

The crisis came to a head at the end of October after accusations that Essebsi supporters armed with sticks blocked rival party members from a meeting of its executive committee.

The rivalry threatens to potentially tear apart the government in a country held up as a rare success story for the Arab Spring after its 2011 overthrow of longtime dictator Zine El Abidine Ben Ali.