The Electoral Commission has pledged to undertake a “thorough review” of what happened in constituencies were people were unable to vote.

Reports came in from across the country of hundreds of people missing the chance to vote as polling stations struggled to cope with increased demand.

There was a sit-in at Hackney polling station in east London. Problems were also reported at Liberal Democrat leader Nick Clegg’s constituency in Sheffield Hallam and at Chester, Fallowfields in Manchester and Wavertree in Liverpool.

No problems were reported at any of the polling stations across Shropshire.

In a statement, the Electoral Commission said: “It is a cause for serious concern that many people who wanted to vote today were unable to do so by 10pm when polls closed.

“Each returning officer is responsible for deciding numbers of polling stations in their constituency and the numbers of electors allocated to each polling station.

“By law, polls must close at 10pm and any voter issued with a ballot paper by 10pm should be allowed time to cast it, but no ballot paper should be issued after 10pm. There should have been sufficient resources allocated to ensure that everyone who wished to vote was able to do so.

“The Electoral Commission will be undertaking a thorough review of what has happened in those constituencies where people have been unable to vote.”

Liverpool City Council said that “due to an unprecedented and unexpected high turnout in the Wavertree constituency, a small number of polling stations ran out of ballot papers in the early evening”.

But the council added: “Additional ballot papers were delivered swiftly to these stations” and “every elector who wanted to vote had the opportunity to do so before polls closed at 10pm”.

John Mothersole, returning officer for Sheffield, 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.”

Politicians from across the different parties expressed their concern at the situation.

Labour Party deputy leader Harriet Harman said that when she left her Camberwell and Peckham constituency, people were still queuing up outside waiting to vote.

“It shows that there has been a high turn-out. We have got to make sure that all the votes are counted.”

Business Secretary Lord Mandelson acknowledged that the situation could lead to legal challenges.

“What the returning officers should have done is brought everyone in and locked the door.”

He said he was concerned about the failure of some people to get in and vote because traditionally Conservatives voted earlier than Labour supporters.

Shadow business secretary Kenneth Clarke said he was “very sorry” to hear reports of problems at some polling stations.

“It’s very worrying indeed,” he told Sky News.

“I feel sympathy for the people who were trying to do the thing they should do, go along and cast a vote.

“I trust somebody sorts out what on earth went wrong and made it so difficult for people to vote.

“I’m obviously not going to leap to any conclusions about what went wrong in Sheffield, Manchester and Islington but the returning officers may owe people an apology if it’s in any way down to them and I think we ought to get an explanation.

“The Electoral Commission might prove its worth by making sure it never happens again.”

By Shropshire Star Election Writer Alex James