Anneli Howard, a barrister who specialises in EU law, said the debacle had infringed EU law, including article 20 of the Treaty on the Functioning of the European Union, which provides that EU nationals have “the right to vote … under the same conditions as nationals of that state [of residence]”.

“If EU citizens are being asked to fill out additional forms that UK nationals are not, that’s discrimination,” she said.

The treaty has “direct effect”, meaning EU citizens can rely on it in domestic courts.

She said that while she doubted a judge would declare the election unsafe because of the errors, individuals might sue for compensation.

A Polish national, Kinga Burger, said: “I went to the polling station today and was turned away and informed about some mysterious form that no one was able to tell me more about. I’m really angry and disappointed I didn’t get to vote.”

Piotr Klaskala, another Polish national, said: “What I find particularly surprising is that I could see my name and current address on the list in the polling station, which suggests that I have registered successfully, but it was crossed out.”