Sarah HallThe election has been marred by controversy after hundreds of people were unable to vote because they were still queuing when polling stations closed.Sarah Hall

The election has been marred by controversy after hundreds of people were unable to vote because they were still queuing when polling stations closed.

The Electoral Commission said it would be undertaking a 'thorough review' of what had happened in constituencies where people were unable to vote.

Voters were turned away from polling stations in Sheffield Hallam, where Liberal Democrat leader Nick Clegg was standing.

Others were turned away from a polling station in Hackney, East London, with some having queued for more than an hour and a half.

There are reports that would-be voters staged a sit-in protest at the building after the ballot boxes closed and police had to be called.

And police were called to a polling station in Manwood Road, Lewisham, south London, where around 300 people had yet to vote by 10pm, Scotland Yard said.

The station there reportedly stayed open for half an hour beyond the 10pm deadline to allow people to vote.

John Mothersole, returning officer for Sheffield, apologised for the problems in his constituency, but said he could not extend the opening times.

He said a large amount of students had turned up to vote without polling cards, which held up the administrative process.

He said: 'We got this wrong and I would like to apologise.'

Angry voters at Sheffield, some of whom had queued for three hours, tried to block the route of the ballot box.

There were also reports of problems in Manchester, Chester, Maidstone, Penistone, Newcastle and Islington, while some polling stations ran out of ballot papers because of the unexpectedly high turnout.

Christine Russell, who is standing for re-election as Labour MP in Chester, said many constituents were turned away because they had not been included on an updated list of people entitled to vote.

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.'

The National Union of Students (NUS) also claimed students in some areas had been unable to vote after being placed in separate queues to other voters.

Elsewhere, hundreds of postal ballots have gone missing in York, with the problems blamed on a printing error and a temporary closure at the local postal sorting office.

Electors in the Liverpool Wavertree constituency were told they had to wait for new forms to be delivered before they could cast their votes.

Meanwhile, counting in Londonderry had to be suspended because of a bomb alert.

A car, hijacked earlier in the city, was abandoned in a car park outside the Templemore Leisure centre.

Did you have problems voting in Norfolk? Email dan.grimmer@archant.co.uk