There are an estimated 5.5 million British expats living abroad including as many as 800,000 living in Spain, but only a tiny portion of them are registered to vote back home.
With the European elections just around the corner and next year’s UK General Election looming, the message from London is: "It's your vote don't lose it!"
The British Government has launched an international campaign to encourage more expats to register to vote. Wednesday has been named as official Overseas Registration Day.
Samantha Mills, head of campaigns at the Electoral Commission said: "Estimates show that there may be as many as 5.5 million UK citizens living overseas, but the latest figures showed that there were only around 20,000 on the UK electoral registers.
"Many of those living overseas do not even know that they may be eligible to vote in some UK elections, so it's important that our campaign is as far-reaching as possible.”
VIDEO: ‘Minister Greg Clark urges British citizens living abroad to sign up to vote
British Citizens who have been registered to vote in the UK and have not spent more than 15 years abroad are eligible to vote in the General Election as well as European Elections and Referendums.
But expats will not be able to vote in the referendum on Scottish Independence which is being held in September.
Wednesday may be the official overseas registration day, voters have until May 6th to download, fill in and return the form, in order to be eligible to vote in the European elections.
To download the form and to find out more information about voting you can visit the website www.aboutmyvote.co.uk
British expats in Spain are currently campaigning for the government to drop the 15-year rule, which means anyone who has lived abroad for longer than that time loses the right to vote.
EU justice commissioner Viviane Reding recently took up the cause and has launched a petition to encourage countries including the UK to change their laws.