City grandee Robert Hiscox started a full frontal attack on David Cameron's campaign.
He called it "corrupt" and accusing Treasury of disseminating "illegal propaganda".
Mr Hiscox, chaired Lloyds of London insurer Hiscox for 43 years until 2013 and is still a honourable member of the board.
He said: "The part the Government has played in the debate is astonishing, Their corrupt statements and illegal propaganda pouring out is something to behold, especially the Treasury documents."
His statement was backed by Tory peer Nigel Lawson and Norman Lamount, both longstanding politicians and ex-finance ministers, when contradicting the Treasury analysis predicting a severe economic shock as a result of Brexit.
Mr Hiscox added further: "The City Institutions support Britain to remain is the EU form part of a "Elite" that are acting in their self-interest.
"All the experts coming out for Remain are a part of the Elite, from Goldman Sachs downwards, they've all bought into it, it's for their own-interest.
"I'm astonished when I meet people from Remain. I'll never understand why they want, in a global race, to tie the UK to 27 other countries, some of which have no legs.
"Why do we want to have millions of rules delivered by an unelected tyrannical elite in Brussels?"
It is the first time Mr Hiscox has his opinion on the European Union openly stated after signing an open letter supporting Brexit with 300 other business leaders and you bet they are one of the most powerful in the City.
