Britain's prime minister outlined who will be allowed to vote in referendum on whether or not the country should remain in the European Union on Monday, opting for rules that exclude most voters from the 28-nation bloc who live in the U.K.

Prime Minister David Cameron announced the parameters ahead of introducing legislation Thursday in Parliament to organize the ballot.

His plans also include a tour of European capitals to press his case that the EU needs to be reformed, hoping that the upcoming vote will focus minds that Britain is determined to enact change. Cameron plans to travel to Denmark, the Netherlands, France, Poland and Germany this week as part of his efforts to talk with all of the leaders of the EU member states before the June European Council late next month.

Under the referendum measure, the vote will be open to the same voters allowed to normally vote in British elections — rather than rules that are used for European Parliament elections. The rules would exclude for example, a French citizen working in London but not qualifying Commonwealth citizens and Republic of Ireland citizens who are eligible to vote if registered. U.K. nationals resident abroad for less than 15 years will also be able to vote.

The question is important because so many non-British EU nationals live in Britain — nearly 2.8 million. Some have argued that they should have a right to vote on something material to their future.

There would be exceptions, most notably in regard to Gibraltar, a British territory. Though situated at the tip of the Iberian Peninsula, Gibraltar resolutely wishes to remain separate from Spain, though public opinion has been staunchly pro-EU.

The chief minister of Gibraltar, Fabian Picardo, praised Cameron for being "true to his word," on giving the territory's residents a chance to vote.

"As a British part of the EU, our voice will be heard as part of the franchise for this seminal exercise in democracy," he said in a statement. "We are working closely with the prime minister and his government to ensure the necessary framework for the EU referendum is in place in Gibraltar at the same time as in the U.K."