In its interim report, the Electoral Commission has suggested that the UK voting law should be changed so that anyone queuing when polls close could still vote.
The call comes after the Commission found that at least 1,200 people were still queuing to vote when polling stations shut at 10pm on election day, 6 May 2010.
Poll access and voting problems were reported in Sheffield, Manchester, Liverpool, Birmingham, Newcastle and various parts of London.
The Electoral Commission report has found that too many voters were allocated to some polling stations, while others had too few staff. There were other administrative problems, too.
Commenting on the Commission's interim report, Peter Facey, Director of the campaigning reform group, Unlock Democracy said: "Failure of this kind is unacceptable in one of the oldest democracies in the world. These debacles could have been a lot worse and should serve as a wake-up call to electoral administrators everywhere."
He continued: "Returning Officers blame high turnout for turning people away, but this excuse does not hold water. Not only did this election see the third lowest turnout since 1945, but it is a returning officer's duty to ensure that everyone who has the right to vote can do so."
"The Electoral Commission are not to blame for the scenes we saw on Polling Day," said Mr Facey. "Their guidance to Returning Officers was clear and they have been warning for years that the electoral administrative system is not fit for purpose. Unfortunately their warnings have fallen on deaf ears. There is a statutory obligation on the Commission to report on the conduct of all elections, however there is not a similar obligation on Government to debate or even acknowledge their recommendations."
The CEO of Unlock Democracy added: "We welcome this Government's pledge in their coalition agreement to speed up the introduction of individual voter registration, however this report should go to the top of the Secretary of State's in-tray. Otherwise, what is the point of having an independent Electoral Commission charged with overseeing elections, if they do not have the powers to ensure returning officers are following their guidance?"
Unlock Democracy runs the Stamp Out Voting Fraud Campaign and successfully lobbied for Individual Voter Registration to be included in the Political Parties and Election Act 2009.
The NGO also called for more powers to be given to the Electoral Commission and lobbied for the requirement that voters show ID in Polling Stations to prevent 'personation'.
Unlock Democracy is one of a range of civil society groups campaigning for democracy, rights and freedoms. It was formed in 2007 as the successor organisation to Charter 88 and the New Politics Network.
Along with Ekklesia and range of other groups, Unlock Democracy supporters have been involved in Power 2010 and the Take Back Parliament (www.takebackparliament/hope) initiative.