City grandee Robert Hiscox has launched a blistering attack on David Cameron's campaign to remain in the EU, dubbing it "corrupt" and accusing the Treasury of disseminating "illegal propaganda".
Speaking to the Press Association, Mr Hiscox, who chaired Lloyd's of London insurer Hiscox for 43 years until 2013, 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 document."
His comments echo those of Tory peers Nigel Lawson and Norman Lamont, who railed against a recent Treasury analysis that predicts a severe economic shock as a result of Brexit.
Mr Hiscox, who is still honorary president at the eponymous insurer, added that City institutions supporting Britain remaining in the EU form part of an "elite" that are acting in their own self interests.
"All the experts coming out for Remain are all part of the elite, from Goldman Sachs downwards, they've all bought into it, it's for their own self-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 detailed his views on the European Union since signing an open letter supporting Brexit alongside more than 300 other business leaders.
Some of the most high-profile City figures calling for Britain to remain in the EU include former M&S boss Lord Stuart Rose, Sir Martin Sorrell and PR guru Roland Rudd.
Mr Hiscox added that the insurance company, currently head-quartered in Bermuda for "tax and regulatory purposes", may move its base back to the UK if Britain votes to leave.
"We decided to move our HQ to Bermuda in 2002 because of the tax and regulatory regime under Labour and under the EU.
"We don't want to bring it back while we're in the EU. If we leave, then it depends on the domestic regime whether we come back or not, but it's possible.
"But we love being in Bermuda, it's a useful place, it's close to the US where we do a lot of business and it makes us feel international. It's not just a tax dodge."
Mr Hiscox was speaking at the White Horse Bookshop in Marlborough, which he acquired two years ago when it was loss making and has since turned around, launching a website in the process.