Britain can survive outside the European Union, Prime Minister David Cameron said on Monday as he denied he was planning to campaign for Britain to stay in the EU regardless of the outcome of reform talks.
"The argument isn't whether Britain could survive outside of Europe. Of course it could," Cameron told the annual conference of the Confederation of British Industry (CBI), the country's main business lobby.
"The argument is how we could be best off," he told the group, many of whose members are concerned about the economic consequences of a possible "Brexit".
Cameron was interrupted by two protesters who stood up and chanted "Voice of Brussels!", reflecting a suspicion among eurosceptics that he has already made up his mind in favour of Britain staying in the EU.
Cameron is to give more detail on Tuesday in a letter to European Council president Donald Tusk on Britain's reform demands ahead of a referendum that is due to be held by 2017 at the latest.
"If I can't achieve them, I rule nothing out," he said, reiterating a warning to EU leaders.
"If these things can't be fixed, then Britain would naturally ask: do we belong in this organisation?
"Is this organisation flexible enough to make sure that countries inside the eurozone can grow and succeed and countries outside the eurozone, like Britain, can get what they want?" he said.
Cameron also repeated that some of Britain's demands would require changing EU treaties -- or at least a binding promise that treaties will be changed.
"What we need to change, some of it does involve changing the treaties," he said.
"What we need to do is get agreement from the other 27 EU countries that that's going to happen... We need to set out that that is legally binding and irreversible," he said.
Cameron has long identified four broad areas where he wants to see reforms -- improving competitiveness, greater "fairness" between eurozone and non-eurozone nations, sovereignty issues including an exemption from the aspiration of ever-closer union and making it harder for migrants to claim benefits.
CBI director John Cridland said ahead of the conference that most but not all business were in favour of continued EU membership.
"Not every single CBI member thinks the same, nor every business thinks the same, but I do have an overwhelming majority of businesses that want to be in a reformed EU and a reform agenda," he said.