However he said be believed the country will be 'freer, fairer and more prosperous' if the public vote 'out' on the June 23 referendum.
Speaking exclusively to his constituents through the Yorkshire Post and The Darlington and Stockton Times, the father-of-two said his years in global business has taught him the key to growth is to remove the bureaucracy of Brussels.
Mr Sunak, who was elected in May, said: "I have spent my business career working around the world, investing in countries like the US, India and Brazil. I have also helped British companies expand internationally. My own experience convinced me that not only can our businesses thrive in these exciting markets, but that they must.
"Since we joined the Common Market, Europe’s share of the word economy has halved and is still falling. Whilst China’s GDP has doubled since the recession, Europe is the only continent in the world (alongside Antartica, that is) that has failed to grow at all."
"Canada, South Korea and South Africa all trade freely with Europe without surrendering their independence. As one of Europe’s largest customers, I see no sensible reason why we could not achieve a similar agreement. Six million jobs in the EU are linked to UK trade and we buy £60 billion more from Europe than Europe buys from us.
"Nationally, only five per cent of businesses export to the EU, yet all businesses are stifled by excessive EU red tape that does everything from mandating the width of our hedgerows to
prohibiting our Government from favouring British produce. It is our small, local businesses that would benefit the most as we remove the burden of Brussels bureaucracy."
Immigration was another key factor his his decision to campaign to leave the EU, and it is understood it was the most debated topic on the doorsteps as he travelled around the Richmond constituency in the run up to the General Election.
He said: "I believe that appropriate immigration can benefit our country. But we must have control of our borders and we can only do that outside of the EU. As an EU member, every one of Europe’s 500 million citizens has a legal right to move here and there is nothing the UK government can do to limit those numbers.
"It can’t be right that unelected officials in Brussels have more say over who can come into our country than you."
The farming community could also manage outside of the Common Agricultural Policy he said, and suggested the creation of a £2.5bn British Agricultural Policy, resourced by a portion of the £20bn saving Britain would make if it were to leave the EU.
He said: "This is a complex and difficult decision for all us. In the end, this is not about my vote or that of any other politician.
"Our future European relationship will be decided by all of you, the British people. I look forward to discussing it with you all over the coming months."