Eurosceptic firebrand Nigel Farage was told off in front of fellow MEPs in Strasbourg after sensationally comparing the EU to the Mafia on Wednesday (5 March).
The former Ukip leader, 53, claimed Britain was being treated like a "hostage" as Brussels considers a £50bn ($62bn) exit bill.
"You're behaving like the Mafia, you think we're a hostage, [but] we're not...we are free to go," Farage told the European Parliament.
But he was stopped mid-speech by Italian EU Parliament president Antonoio Tajani, who described Farage's remarks as "unacceptable".
Farage, to jeers from his fellow MEPs, adjusted his language to "gangsters".
The undiplomatic exchange comes just a week after Theresa May invoked Article 50 of the Lisbon Treaty and triggered the two-year-long divorce talks with the EU.
The Conservative premier recently failed to rule out an exit bill for the UK when grilled by the BBC's Andrew Neil. "There has been a lot of speculation and a lot of comments, we're not in the negotiations yet, we will start those formal negotiations soon. We've done the first step which is triggering Article 50," May told the veteran journalist.
"The UK is a law-abiding nation and we will look at the rights and obligations that we have."
An online ICM poll for The Guardian, of more than 2,000 people between 31 March and 2 April, found that just 10% of respondents thought an exit bill of £20bn – the highest amount asked by the pollster – was acceptable.