Could Britain end up leaving the EU? The key questions

Charles Grant, director of the CER argues that EU governments will not grant treaty opt-outs to Britain because of fears that it could gain "an unfair competitive advantage" within the single market and encourage other countries to follow Britain's pick-and-mix example.

Mr Grant sees a scenario in which Mr Cameron returns from negotiations with a package that fails to placate his eurosceptics, who embark on a campaign of withdrawal in the referendum campaign. ...Mr Grant believes that even if the prime minister fails to achieve a breakthrough deal in negotiations after victory at the next election, a pro-EU campaign led by the Labour and Liberal Democrat could succeed. But he says it could be more difficult for Labour, if it wins the 2015 election, to triumph in a referendum - assuming it follows Mr Cameron's example and agrees to hold one. This is partly because Labour is not seeking a new deal with the EU.