According to official statistics, more than 200,000 Lithuanians live in the U.K | Sean Gallup/Getty Images Lithuanians to vote in referendum prompted by Brexit Campaigners are worried that not enough citizens are aware the vote is happening.

Lithuanians will decide Sunday on whether to change their constitution to allow dual citizenship in a referendum prompted by Brexit. Campaigners are worried though, that misinformation and apathy could deny them a victory.

The country, which has a population of 2.8 million, has more than 10 percent of its citizens living in another EU member state; 700,000 citizens have moved abroad since 1990.

Many Lithuanians left for EU member states with higher wages after the 2008 global economic crash. The country's aging population has led politicians to call for young emigrants to return.

More than 200,000 Lithuanians live in the U.K. according to Eurostat. With freedom of movement, the lack of dual citizenship was never an issue. But now that the U.K. is leaving the EU, many are worried that thousands of citizens could choose to give up their Lithuanian passports and take up British citizenship.

The vote only concerns amending the constitution so that Lithuanian citizens by birth do not lose their citizenship when they acquire the passport of another country.

“Most Lithuanians want to go back home at some point. It’s important they have the option" — Dalia Asanavičiūtė, chairwoman of the Lithuanian Community in the UK

Dalia Asanavičiūtė, chairwoman of the Lithuanian Community in the United Kingdom, says the dual citizenship debate did not begin because of Brexit, but it had sped up the process.

“Most Lithuanians want to go back home at some point. It’s important they have the option,” she said. “It would be very harmful to the country to make them choose.”

But opinion polls show that less than half of voters plan to vote for the change, according to news website LRT.

And an online survey of over 1,000 Lithuanians in the U.K. commissioned by the Lithuanian City of London Club (LCLC) found that around 26 percent are willing to take British citizenship.

Current exceptions to the dual citizenship rule include people who left or were deported from the country before 1990, when it was under Soviet rule.

The referendum is taking place at the same time as the first round of the presidential election in which incumbent President Dalia Grybauskaitė is standing down after reaching the term limit of two consecutive terms.

Postal voting started at the beginning of May for Lithuanians living abroad, while early voting in the country began on Monday morning and will end Friday evening, preceding the polls opening on Sunday.

Marius Raugalas, chairman of the LCLC, said the government and opposition parties agreed to hold the referendum in “a rare moment of unity.” But the government did not set the May 12 date until March.

"This is a ridiculously short time frame for a campaign about changing the constitution," Ieva Steponavičiūtė, chair of the board of the Lithuanian Youth Association in the United Kingdom, said. She added that the short campaigning time has made it difficult for activists and the government to battle misinformation.

There is also a high barrier to it passing. More than 50 percent of all eligible voters must vote in favor for the proposal to be adopted.

Those against the referendum say that Lithuanians could use dual citizenship to evade mandatory conscription; that it would harm national security; and that it is unpatriotic. Laurynas Kasčiūnas, an MP with the center-right Homeland Union party, said he will be voting against the change because it could in fact encourage more young people to leave. “We should not be talking about a global Lithuania. We should be thinking about how to get people to come back to Lithuania.”

it’s hard to reach all the Lithuanians living abroad because they don’t all follow the same media" — Marius Raugalas, chairman of the Lithuanian City of London Club

Despite the referendum restricting dual citizenship to countries in the EU, European Economic Area, NATO and the OECD, there are also concerns it could lead to Russians gaining a Lithuanian passport.

To increase turnout, community groups in the U.K. have used Facebook and leaflets to spread the word, but there are fears it will not be enough. “Most [expats] have never voted from abroad,” Raugalas said. “And it’s hard to reach all the Lithuanians living abroad because they don’t all follow the same media.”

While a government-commissioned poll shows 65 percent of respondents intend to vote in the referendum, Steponavičiūtė said much of the push for discussion has been carried out by the diaspora itself, meaning Lithuanians back home may not be swayed to vote for the change.