Voters were turned away from polling stations in Sheffield Hallam this evening, where Liberal Democrat leader Nick Clegg was standing.
A number of voters, mainly students, were turned away after attempting to vote shortly before the 10pm deadline because they did not have polling cards, a Sheffield City Council source said.
John Mothersole, returning officer for Sheffield, apologised to residents who were unable to vote.
He said: “We got this wrong and I would like to apologise.
“We were faced with a difficult situation with the numbers of people, and a large amount of students turning up to vote without polling cards.
“This made the administration process of ensuring the correct person was given a ballot paper much longer.
“The only remedy, which we could not take, was to extend the voting times.”