Prime minister David Cameron has called a referendum on the UK's membership of the European Union in the middle of the Euro 2016 tournament.
British voters will take to polling stations to vote on the yes-no issue on Thursday, June 23, a date which also clashes with the Glastonbury Festival.
With England, Wales and Northern Ireland all participating at the tournament in France, more than 100,000 voters are expected to be out of the country, with a further 150,000 revellers due to be away from home for the annual music festival.
A spokeswoman for the Electoral Commission urged fans attending Euro 2016 and Glastonbury on June 23 to register to vote by post or proxy instead.
