Former London mayor Boris Johnson and justice secretary Michael Gove have hit out at the European Union's effects on business, while accusing the government of misleading the public on the economy.
In a 2,000 word letter to Prime Minister David Cameron, which is also signed by Labour's Gisela Stuart, the Leave campaigners played down business support for the EU.
And the Brexiteers argued that European nations are failing to foster innovative new technologies and business models.
"The EU lacks the networked relationship between great universities, entrepreneurs and venture capital that generate economic breakthroughs.
"That is why there have been no EU equivalents of Apple, Uber, Amazon, Netflix, Google or Facebook. Indeed the EU’s whole regulatory structure works against innovation," the letter said
“EU membership helps some people and some businesses but they are disproportionately those with power and money."
“The reality of the ‘Single Market’ has not even closely matched what we were promised a quarter of a century ago. EU membership makes it impossible to control immigration and this is putting enormous strain on public services and is corrosive of trust in politics," the letter said.
The Leave camp also condemned Treasury predictions of households losing out to the tune of £4,300 each by 2030 in the case of Brexit, calling the forecasts “bogus” and “economically indefensible”.
A Remain campaign spokesman hit back: “Leaving Europe and the single market would wreck our economy, which would be disastrous for innovative UK businesses.
“Last week 60 start-up investors warned that the economic shock of leaving Europe would hit the sector hard, saying ‘start-ups would be the biggest victims’. The tech industry also agrees that we are stronger in Europe with over 70 per cent of UK tech firms supporting continued EU membership."
It comes as a poll of more than 900 Conservative members has found that increasing numbers blame David Cameron and George Osborne for divisions within the party.
Eurosceptic Tory blog Conservative Home last month found that just over half of Tories blamed the pair, but in its latest survey, the site has now found that 60% point the finger at the Prime Minister and the Chancellor.
At the same time, those blaming former Johnson, Gove and Leave campaigners for the mood of the Conservative party has reduced over the last month, from 16 per cent to 15 per cent.
And those who said both sides should share the blame increased from 11 per cent to 13 per cent.
However, the most dramatic move came in the numbers who felt that there was no danger to party unity.
One in five told the Tory site that this was true last month, but almost a third of that group have no changed their minds, at just 13 per cent of the total.