The boss of CMC Markets and former Tory party treasurer Peter Cruddas has said Britain should "walk away" unless it can get the right EU deal, and attacked the Lords and rebel MPs for frustrating Brexit efforts.
Mr Cruddas - a self-proclaimed major Brexiteer - accused peers of seeking to block Brexit by backing amendments to give Parliament a "meaningful vote" on the final deal and how to proceed in the absence of a withdrawal agreement.
The spread betting tycoon, 64, told the Press Association no deal was better than a bad deal for the UK and claimed peers had overstepped the mark after seeking to push through 15 amendments to the Brexit Bill.
He said: "I was very disappointed with the Lords - it seems to me they exceeded their authority.
"It's clear to me they were trying to block Brexit, not trying to amend Brexit terms for the sake of the country."
He added that rebel MPs were "trying to go against constituents".
"It's madness," he said.
"We should just get on with it - business needs certainty."
But he insisted the right deal was vital.
"I'm a supporter of walking away unless we get the right deal for the country," he said.
Remaining tight-lipped on Theresa May's handling of the negotiations, he instead pointed the blame on rebel MPs, Peers and the EU.
"Politics is getting in the way of reality," he said.
Last week Mrs May secured victory in a critical commons vote, defeating an amendment tabled by Dominic Grieve over a "meaningful vote" for MPs on the UK's exit.
The CMC chief's comments come as Airbus becomes the latest firm to warn that it could pull out of the UK in the event of a "no-deal" Brexit, joining Square Mile firms who have already started shifting staff out of the City.
But Mr Cruddas - ranked 206th in this year's Sunday Times Rich List and one of the biggest donors to the Vote Leave campaign - believes the City will hold firm on its position as a global financial centre after Brexit.
He said fears over an exodus of bank staff were overplayed after the EU referendum, but said the City needs to be able to trade freely with the EU even if firms lose their so-called passporting rights should the UK leave the single market.
"I would like us to trade freely with our Euro partners as we do with the other countries around the world - the US, Middle East, Far East - and I see no reason for it to be any different."
CMC itself is putting in place contingency plans with a European headquarters in Frankfurt to run alongside its London HQ, but Mr Cruddas sees little need to shift staff to Germany, given its online focus.
Founded by Mr Cruddas with a £10,000 investment in 1989, CMC began life as a foreign exchange broker and is now a spread betting giant with a stock market value of nearly £600 million.
But Mr Cruddas is keen to position the group as a "technology-driven business", rather than a contracts for difference and spread betting firm.
It signed a stockbroking partnership with ANZ Bank in Australia last year, using its bespoke technology to provide a share trading platform, which will see over 650,000 clients moved on to CMC's database by delivery in September.
Dubbed by Mr Cruddas as CMC's "Ocado moment" - referring to the online grocer's deals to provide technology platforms for other retailers - it is where he sees the firm's biggest growth opportunity.
With no competitors in this space, he hopes to sign further similar deals within the next year.
CMC is also opening an office in Malaysia and expanding across the Middle East, with plans for a base in Dubai.
And China is in the group's sights for expansion, with CMC ready to pounce once the Chinese market begins to opens up.