At the end of 2014, Jean-Luc Mélenchon and Martine Billard resigned, and the party leadership was then collectively ensured by the national secretariat.

In 2016, in view of the presidential and legislative elections of the following year, Jean-Luc Mélenchon formed a new movement, La France Insoumise, that the Left Party helped to animate.

The party advocates eco-socialism as an alternative to capitalism, stating that: "Ecosocialism makes it possible to contribute in an exemplary way to the fight against the looming ecological catastrophe, through a major transformation planned over time in modes of production and consumption.

Our ecosocialism aims for human emancipation and involves breaking with the domination of the capitalist logic of maximum and endless accumulation.

[21] Around 90 locally-elected officials (municipal, regional and general councillors), including two members of the Council of Paris, initially joined the party.