"This is a big decision for our country, one that is about the future of the United Kingdom. That's why we think it's important that it is British, Irish and Commonwealth citizens that are the ones who get to decide," The Telegraph reported on Sunday, citing an anonymous government source.
UK Prime Minister David Cameron had pledged to held a referendum on EU membership if his Conservative Party won the May 7 election.
The UK prime minister seeks to revise Britain's relations with the European Union ahead of the referendum by reforming the system of contributions to the bloc's budget and granting broader powers to member-state governments to control migration levels.
The United Kingdom has been a member of the European Union since 1973. According to an Ipsos MORI poll, as of October 2014, 61 percent of Britons polled wanted to stay with the bloc, while 39 percent of respondents supported ending membership.