Nigel Farage told fellow MEPs "you're not laughing now" as he was barracked and booed at an emergency meeting of the European Parliament to discuss Brexit.
At a highly charged session in the Brussels chamber, EU Commission president Jean-Claude Juncker also questioned why the Ukip leader had attended the session following the Brexit vote.
Sinn Fein MEP Martina Anderson has said if English votes "drag us out of the EU that would be like Britannia waves the rules", as she raised concerns over a border between Northern and the Republic of Ireland.
Speaking in the European Parliament, she said: "We accept, we respect and we will defend the wishes of the people of the north of Ireland.
"However if English votes drag us out of the EU, that would be like Britannia waives the rules.
"There was a democratic vote, we voted to remain. I tell you, that the last thing the people of Ireland need is an EU border with 27 member states stopped right in the middle of it."
The Democratic presidential candidate may also have shown his cards on his choice of running mate.
The US president also shared a post on Twitter accusing Dr Anthony Fauci of misleading the public over hydroxychloroquine.
Fears over an impending second wave of coronavirus dominates Wednesday’s front pages.