Videos captured from the scene show three people lying on the ground coming under attack from a larger group, all of them wearing hoods.
A feminist anti-immigration group called Némésis said Deranque had been outside the venue to protect its members. Némésis has blamed Young Guard for the attack – an allegation it denies.
Government spokesperson Maud Bregeon has urged the party to suspend Arnault from its parliamentary group because of the MP’s links to Anti-Fascist Young Guard, which has been blamed for the violence a short distance from Sciences Po University in Lyon.
A minute’s silence was held in the National Assembly on Tuesday for the young activist, and politicians lined up to criticise the radical-left leader and his colleagues.
Jordan Bardella of the far-right National Rally said Mélenchon had “moral and political responsibility” for what had happened and even former LFI MP Alexis Corbière called on the party to take stock politically of what had happened.
Sébastien Lecornu said that “without undermining the presumption of innocence” LFI had to “clean up” its statements, ideas and its ranks fast.
Mélenchon hit back, saying he refused to take lessons from Lecornu.