An online service set up to help EU citizens in the UK to register to vote in the European parliamentary elections has been shut down after it emerged it was not working properly.

Registertovote.eu, which was promoted by some MPs on social media, offered a form to fill in online and said it would submit the required paperwork to electoral authorities to allow people to vote.

In order to take part in the election in the UK on 23 May, EU citizens from countries other than the UK, Ireland, Malta and Cyprus have to fill in form UC1/EC6 and submit it to their local electoral office before midnight on Tuesday 7 May.

Registertovote.eu was set up by four people at ChangeLab, a co-operative that does digital work for trade unions and campaign groups, after publicity about the low number of EU citizens who had registered to take part in the election.

The Registertovote.eu site as it appeared on Friday Photograph: Registertovote.eu

The service was promoted on Twitter by the Change UK MP Sarah Wollaston and the Liberal Democrat Tom Brake. “I urge all EU citizens living in the UK to make sure they have registered to vote. You may lose all voting rights after Brexit – so use your vote while you have it,” Brake wrote.

However, electoral officials said they did not endorse the service. They said the issue was not about supplying the information digitally, but that the service was not supplying all of the information legally required.

The Electoral Commission requested the site be closed down as it did not correctly reflect the advice its owners had been given. It was closed by 3pm on Friday.

The Electoral Commission said: “We urge EU citizens that want to vote in the European parliamentary elections in the UK to only apply to register to vote through their local council or official websites. We welcome efforts by campaigners to encourage eligible electors to register to vote. However, our advice to anyone not yet registered is to only apply directly at www.gov.uk/registertovote.”

It said of the closed site: “We have concerns about their ability to ensure electoral registration officers will receive completed applications before the deadline. We are also concerned about their use of people’s data and have referred these websites to the Information Commissioner’s Office.”