LONDON — Prime Minister David Cameron and his Liberal Democrat deputy, Nick Clegg, clashed Thursday on whether the possibility of Britain leaving the European Union within five years risks putting off investors and damaging the economy.

Clegg, who leads the pro-EU Liberal Democrats, distanced himself from his Conservative coalition partner’s plans to repatriate powers from the EU. Cameron promised voters a referendum Wednesday by late 2017 on whether to remain in the EU on new terms or leave the 27-nation bloc, saying he will make the case for staying.