There is a "huge risk" that Britain could leave the European Union in the coming years, Italian Prime Minister Enrico Letta warned on Tuesday, dpa reported.
"In European Union countries we are under-recognizing the risk of having in two or three years the UK out of Europe," he told an audience at the Chatham House think tank in London. "In my view it's a huge risk."
Under pressure from the strong eurosceptic wing of his Conservative party, British Prime Minister David Cameron has promised to renegotiate Britain's EU membership and put the results to a referendum by 2017.
Letta, a former member of the European Parliament, was speaking at the beginning of a two-day visit to Britain. He was due to meet Cameron on Wednesday.
"A European Union without the UK on board is not a European Union," he said. Without Britain, the bloc would be "less open to the world, less liberal in its economic approach, less innovative."
Rome and London should work together to reform the EU, he said, which needed "a change of gear." The two countries should also push for the completion of the single market, including in the areas of services, energy, telecommunications and the digital economy, he said.
The single market, the EU's main attraction for Britain, was the "single most important aspect" of the bloc and was the "best engine we have to restore growth in Europe," Letta said.
The bloc should also find a way to "accommodate" members of the eurozone that want to move towards further political and economic integration, as well as those that are "satisfied with the single market," he said.
In world where "size matters," individual member states could not "go it alone," he warned. "Not even Germany has the economic and politcal strength to exit the (economic) crisis with its own forces."