Ukip MEP Mike Hookem has avoided suspension from the party over the altercation which left former leadership contender Steven Woolfe in hospital.
Mr Woolfe quit the party and abandoned his leadership bid after the fracas with Mr Hookem in the European Parliament building in Strasbourg on 6 October.
European Parliament president Martin Schulz has referred the “regrettable” incident to the French police “given the seriousness of the reported facts and their possible criminal implications”.
Ukip has now concluded its internal inquiry into the incident and said it was “impossible” to determine what happened as there were no eye witnesses.
Party chairman Paul Oakden said he was “appalled” by the situation and revealed he “strongly considered” suspension as an option.
But he stressed that Mr Hookem apologised and showed regret for joining Mr Woolfe in the ante room where the altercation took place outside a meeting of party MEPs.
Mr Oakden also said Mr Hookem, “whilst foolish, was not the instigator of this incident or subsequent press coverage and as such cannot be held principally responsibly for either taking place”.