Martin Schulz has reported Steven Woolfe and Mike Hookem to the French police over an "altercation" between the two Eurosceptic MEPs. The European Parliament President had already launched an investigation into the Strasbourg incident on 6 October.
Woolfe was hospitalised after the incident and later claimed Hookem, a former soldier, had punched him. Hookem, who has represented Yorkshire and the Humber in the European Parliament since 2014, has vehemently denied the allegations.
But Schulz weighed into the row today, telling MEPs he had "no doubts" of Woolfe's account of the incident. The comments come after Woolfe's dramatic resignation from Ukip.
The former migration spokesman was favourite to succeed Nigel Farage after Diane James quit the role following just 18 days in the job.
Woolfe, a former City of London barrister, will now sit in the European Parliament as an independent.
Hookem said he wondered if Schulz would repeat his "defamatory claims" outside of the European Parliament, where MEPs do not have immunity from libel law.
Woolfe had already reported Hooken to the French authorities, while Ukip's internal investigation into the "altercation" is yet to be released. A spokesman for Woolfe declined to comment today when approached by IBTimes UK.
The development comes as Ukip hopefuls battle it out to become the party's next leader. Paul Nuttall, a former deputy leader of Ukip, is favourite, with ex-deputy chairman Suzanne Evans second and former Farage aide Raheem in third place.
The candidates must submit their applications to the party by midday on 31 October.
The hopefuls will need 75 signatures from at least 10 branches to be eligible and need to pay a deposit of £5,000 ($6,122). Ballots will be sent to Ukip members "shortly after" 11 November.
A new leader will be in place by 28 November, according to Ukip's National Executive Committee.