"Countries in Europe have their histories, their traditions, their institutions, want their own sovereignty, their ability to make their own choices, and to try and shoehorn countries into a centralised political union would be a great mistake for Europe, and Britain wouldn't be part of it," Mr Cameron told CEOs and investors in a speech at the World Economic Forum in Davos.
Mr Cameron's speech at Davos comes a day after he promised Britons a vote on quitting the European Union, saying the country would have a referendum by the end of 2017.
"Britain is a major European player on all of the issues where Europe needs to act - being more competitive, fighting terrorism, combating climate change - we are right out there leading the arguments, making the arguments."
"And that is the sort of political action that we need. But a centralised political union? Not for me, not for Britain," Mr Cameron said.