Asked if Britain would be better off quitting the European Union, Mr O’Neill said his thinking had radically changed in recent months. “Given the speed of the growth of China and others, I don’t think we can afford to have our opportunities constrained by decisions that may be taken to ensure the United States of Europe,” he said. “It’s a trade off and it’s less clear than it used to be.”

He argued that by the end of the decade, Britain’s trade with the BRIC countries of Brazil, Russia, India and China, will account for 17pc of total exports. “While our position with EU and eurozone is of number one importance, we should not get blindsided as that being the key thing for our export future. Our big future for exports this decade... is going to be other parts of the world, particularly China.”

Mr O’Neill said that western economies still underestimate the scale of the growth of the BRICs as well as the next four big emerging market economies of Indonesia, Mexico, Turkey, South Korea. “This decade, those eight countries will contribute as much to the dollar value of world GDP as that of the US and euro area put together, twice,” he said. “So in the context of what’s really going on in the world, the surprisingly strong showing of the Five Star movement in the Italian elections, the shenanigans known as Washington; these are not for manufacturing exporters the key things that matter in the world, it is the emerging market economies.”

There were now "some signs that we can turn our economy round", [Cameron] said, citing the reduced deficit, low interest rates, and higher exports to emerging economies like Brazil, Russia, India and China.