An estimated 3.5 million Britons living overseas will from Tuesday be eligible to vote in United Kingdom general elections, in one of the biggest increases in the country's electoral franchise in a century.
The expansion in the electorate follows a change in the law, approved by parliament in 2022, scrapping a previous curb on U.K. citizens voting if they had lived overseas for over 15 years.
Implemented ahead of an election set for later this year, it is the most significant change to the voter rolls since a 1928 law granted women equal voting rights, and a 1969 move to lower the voting age to 18 from 21.
Britons worldwide will now be able to register to vote online, regardless of how long they have been overseas.
Under U.K. election law, once registered overseas voters will also be permitted to donate to political parties and campaigners.
Around 233,000 overseas voters were registered for the last election in December 2019, a significant Brexit-attributed bump on the numbers seen in previous contests.
The government estimates that Tuesday's change could enfranchise around 3.5 million people — nearly triple the 1.3 million votes that was the winning margin in the 2016 referendum on European Union membership.
It is also greater than the difference in the vote totals for Britain's two main parties — the Conservatives and Labour — in five of the last six general elections.
But U.K. elections ignore the parties' overall vote counts, instead electing lawmakers under the first-past-the-post system in 650 individual constituencies.
It remains unclear how many of the newly eligible 3.5 million U.K. citizens living overseas will successfully register to vote.
They will need to provide details of the address and time they were last registered to vote or living in Britain.
Local authorities, who are responsible for the electoral roll in their areas, must be able to verify an applicant's identity and past connection to the area, according to the Electoral Commission.
Unlike some countries, there is no provision for in-person voting overseas, and all ballots have to be cast by mail or by using a proxy in the U.K.
The Electoral Commission is launching a publicity campaign and working with partner organizations to raise awareness of the rule change.
"We know there are eligible voters in every corner of the world, so we're calling on those with friends and family abroad to help spread the news," communications director Craig Westwood said.
Research by Britain's Office for National Statistics suggests the largest numbers of British emigrants are in Australia, New Zealand, the United States, Canada and European Union member countries.
