France’s opposition Socialist party was tearing itself apart on Sunday as rival camps in this weekend’s leadership election traded insults and accusations of cheating after a hotly contested vote left the party deeply divided.

Party insiders warned that the risk of a permanent split was greater than ever after the Friday poll which gave a razor-thin victory to the party traditionalist Martine Aubry over former presidential candidate Ségolène Royal. The margin was just 42 votes out of 134,784 valid ballots cast.