Guy Verhofstadt, told the Ukip leader: “Finally we will be getting rid of the biggest waste in the EU budget – that we have paid for 17 years of your salary.”
The Belgian politician, who became an MEP after heading three governments over almost a decade, condemned a “climate of fear” generated by the campaign ahead of the EU referendum.
Addressing the European Parliament in English, he said he respected the UK’s vote to leave the EU but was concerned about the reasons for it.
“It’s my feeling that it’s not so much the choice they have made that is hard … what makes it so hard is the way it succeeded,” Mr Verhofstadt said.
“The absolutely negative campaign, the posters of Mr Farage showing refugees like in Nazi propaganda.
“I was never told that it was possible that somebody in this house should do a thing like that.
“The lies also on migration. The lies on ‘oh Turkey will join the union next week’. Or the lies on the £350m that should return immediately to the National Health Service. And now don’t go back to the National Health Service.
“It’s that climate of fear that has been created, of negativism that has been created – that is the most shocking thing that has happened in Britain – not the choice of the people, because the choice of the people is democracy.”
Mr Verhofstadt pointed to losses in the stock market and the plummeting value of the pound following Friday’s results, quipping: “It goes down when you speak Mr Farage, wait a little bit … and every time Boris Johnson speaks, the more the British currency slips.”
He went on to call for Article 50 to be immediately invoked to start the process of a Brexit to end the “toxic” uncertainty affecting EU economies and relations.
“It is an act against the bickering of the Tory leadership and against the selfishness of one man (Mr Johnson) who was ready to do anything, even to sacrifice the voice of 70 million British citizens to become Prime Minister of the UK - or should I say Prime Minister of the dual kingdom of England and Wales,” he said.
“We both, British and Europeans, cannot afford to be stuck in limbo.”
Mr Farage was booed by hundreds of MEPs in the chamber after telling them they had “never done a proper job in your lives” and threatening “consequences far worse for you than us” if the EU rejects future trade deals.
The Ukip leader was laughed at as he hailed his own success, hitting out at the EU for being a “political project in denial”.
Jean-Claude Juncker, the President of the European Commission, asked Ukip MEPs why they were present for the session, despite wanting to exit the European Parliament.
He said: “You were fighting for the exit, the British people voted in favour of the exit, so why are you here?”
A resolution was passed calling on the UK to implement Article 50 and start exiting as soon as possible, but the Brexit must be formally approved by Parliament.
David Cameron was heading to an awkward meeting with EU leaders on Tuesday.
In the first session since the UK voted to leave the 28-nation bloc, he was due to discuss the implications of the Brexit as market volatility continued.
The Prime Minister, who led the Remain campaign, resigned on Friday but will not leave his post until a new Conservative Party leader is elected in October.
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