French police will now investigate an alleged scuffle between two members of the UK Independence Party in the European Parliament building in Strasbourg.
Steven Woolfe was hospitalised with a head injury earlier this month.
His colleague Mile Hookem denies punching him outside a party meeting.
EU Parliament President Martin Schulz says an internal inquiry he commissioned has been unable to reconcile the accounts of the two UKIP members.
Woolfe has pulled out of the race to succeed fellow MEP Nigel Farage as leader and quit the party.
He said it had become “ungovernable” since securing the ‘Brexit’ referendum result.