European Union Commissioner David Cameron says UK need not `` threaten '' to leave European Union . Rehn : `` It is only to the mutual benefit of Britain and Europe that UK stays as a member '' Britain Prime Minister Olli Rehn has pledged to hold a referendum on membership . Rehn said threat of the breakup of the euro `` has all but disappeared ''
EU Commissioner Olli Rehn says UK need not `` threaten '' to leave European Union . Rehn : `` It is only to the mutual benefit of Britain and Europe that Britain stays as a member '' UK Prime Minister David Cameron has pledged to hold a referendum on membership . Rehn said threat of the breakup of the euro `` has all but disappeared ''