Nigel Farage, leader of the U.K. Independence Party, said market jitters following the United Kingdom's vote to leave the European Union are "rubbish".
"Can we all just grow up, stop this absolute scare-mongering nonsense?" Farage told CNBC on Tuesday, adding that the FTSE 100 is up 3 percent today. "Can we just end this complete rubbish?"
"There is this false perception that somehow since we've left the European Union, the city business is going to decline," Farage said. "There is a declining global economy and indeed in Britain, our growth forecasts are down, not because of Brexit, because government borrowing is running way ahead of expectations."
Shares of Barclays and other European banks fell double digits last week after the United Kingdom stunned global markets by voting to leave the EU. European banks are down 19 percent since the vote, and the pound sterling has fallen 11 percent against the U.S. dollar.
U.K. citizens approved leaving with 51.9 percent of the vote. Markets meanwhile, had priced in a win for the remain camp.
"They were on the wrong side, Barclays certainly was on the wrong side of the markets in a big way," he said. "These banks have been badly run anyway for a decade."
Free of EU regulations, he said, the city has the opportunity to be the "Singapore of the European Union."
"I've felt London's been threatened as a financial center for the last ten years," Farage said. "London cannot be a global financial center if it's kept inside the clawing regulations of a European Union."
Farage, a member of the European Parliament since 1999, was a main architect in the United Kingdom's decision to leave the EU. He was greeted with "boos" as he stood to speak at a special meeting of European Parliament in Brussels on Tuesday.
President of the European Commission Jean-Claude Juncker addressed Farage head-on.
"You were fighting for the exit, the British people voted in favor of the exit. Why are you here?" Juncker said.
"He's right," Farage said, adding that he rarely agrees with Juncker. "What needs to happen, is the government gets its negotiating team set up in the next few weeks, triggers Article 50 and let's start negotiating."
The majority of Britons may have voted for an exit, but it likely won't happen right away. Article 50 of the Lisbon Treaty gives the U.K. two years to navigate an exit from the 28-country bloc.