Hundreds of angry EU27 citizens have been turned away from UK polling stations today, say campaigners.
People have been taking to Twitter to share their stories of rejection.
The hashtag #DeniedMyVote has been trending since Thursday morning, just hours after polls opened for the European Parliament elections.
The3million group, which represents EU27 citizens in the UK, said authorities' unwillingness and incompetence had denied them a vote.
The Electoral Commission said the fact elections had been organised at such short notice had made it difficult to make citizens aware of what they needed to do to vote.
'This is ‘my’ EU member state'
Agata Patyna, a human right and immigration barrister, said on Twitter that she had been turned away from a polling station on Thursday morning.
“Told I should vote in my EU member state. Called local council yesterday, they confirmed I could vote. Called again today. Apparently, the council had no time to send out forms to all EU residents. Nothing they can do now," she wrote.
“To clarify, I registered before the deadline. Have been here since 2005. Voted many times before. This is ‘my’ EU member state,” she added.
'Follow up with your council'
The European Parliament elections are organised by national electoral authorities, so many voters have taken to their local councils in the UK to file complaints.
Marta Federici took to Twitter this morning to report that she and her husband had been marked "as ineligible to vote at the polling station". She reached out to the Lewisham Council to flag the issue and they rectified the error and both were allowed to vote.
"Follow up w/ your council if you find yourself unexpectedly marked as ineligible to vote! #dontgiveup NOT #DeniedMyVote #EUelections2019," she posted.
'I have voted in every election ... but not today'
German national Johannes Hoffmann, 49, told Euronews that he showed up at his polling station and was turned away.
He said he sent the UC1 form around April 20, which should have left enough time to meet the May 7 deadline but the Islington electoral services told him they never received the form.
"I’ve been living for nearly 25 years in this country and have voted in every election I was eligible for since.
"But not today as my form was lost in the post, so I’m told," he wrote on Twitter.
What did the3million group say?
"We have been contacted by hundreds of angry EU citizens from all around the country who were turned away from polling stations when they showed up to vote in the European parliamentary elections today.
"These European elections are significant to so many EU citizens as this might potentially be the last nationwide vote before our voting rights will be downgraded to potholes and bin collections in local elections.
"The Electoral Commission but also local authorities must urgently answer why so many people were denied their right to vote.
"It is outrageous that the incompetence and unwillingness of the government and the Electoral Commission have denied these people a vote.
"The3million is calling for a full investigation of this democratic disaster that has disenfranchised many of the European citizens most affected by the outcome of these elections.
"In the meantime, we urge all EU citizens who were denied their vote to complain to the Electoral Commission and speak out on social media using the hashtag #DeniedMyVote."
What are the rules for EU nationals voting in the UK?
In order to vote, EU nationals (except those from Cyprus, Ireland, and Malta) living in the UK needed to be registered to vote and also complete a voter registration form guaranteeing that they will not vote in their home country. The deadline to submit this form to a local electoral services department at their council was May 7.
Instructions and forms were available on the official website for the European elections, but some voters seem to be unaware of the extra bureaucratic hoop they needed to jump through, with many showing up at polls expecting to vote and being turned away.
“We understand the frustration of some citizens of other EU Member States, resident in the UK, who have been finding they are unable to vote today when they wish to do so," an Electoral Commission spokesperson told Euronews.
Adding that the very short notice of the UK's participation impacted the "time available for awareness of this process amongst citizens, and for citizens to complete the process".