UK votes in electoral system referendum
London - Britain voted on Thursday on changing the electoral system in its first national referendum in more than three decades following a bitter campaign that put the ruling coalition under strain.
Opinion polls indicated the electorate would opt to keep the first past the post system, in which the candidate with the most votes wins, shunning a switch to the alternative vote (AV) in which candidates are ranked by preference.
Prime Minister David Cameron is leading his centre-right Conservative party in opposing the change, while his deputy, Nick Clegg of the centrist Liberal Democrats, is a strong supporter of the "Yes" camp.
A result is not expected until late on Friday.
A Guardian/ICM poll on Thursday predicted a 68% "No" vote with just 32% in favour of changing the system, while a YouGov poll published in The Sun forecast 60% "No" and 40% "Yes".
The nationwide referendum is taking place alongside elections for the devolved national assemblies of Scotland, Wales and Northern Ireland, plus for local authorities in England and Northern Ireland.
Low turnout expected
Britain has only held one nationwide referendum in recent times, when voters on June 6 1975 backed the country's continued membership of the European Economic Community.
Turnout in 2011 is likely to be low, as both sides have struggled to get their message across amid the clamour of the royal wedding between Prince William and Kate Middleton, followed by the death of Osama bin Laden.
But nearly one year after a general election that created an unlikely marriage between the Conservatives and the Liberal Democrats, the war of words between the coalition partners has still garnered headlines.
The Conservatives only agreed to hold the referendum after Clegg's Liberal Democrats, normally the third-placed party in elections, made it a condition of joining forces to form a government.
But Clegg has recently accused the "No" camp of "lies" and Liberal Democrat energy minister Chris Huhne said they ran a Nazi-like campaign, in a row that spilled over into a testy confrontation in Tuesday's weekly cabinet meeting.
Cameron - whose government is pushing through harsh public services cuts to tackle a record deficit left by the previous Labour government - sought to play down the row on the eve of the polls.
Current system 'simple'
He said that while there was disagreement, "the reason for having a coalition government, coming together, sorting out this country's problems in the national interest, is as good an argument today as it was a year ago".
At stake is the fundamental question of how Britain elects its lawmakers.
Under AV, voters rank candidates standing in a parliamentary constituency in order of preference, with the lowest-scoring candidate eliminated through a series of rounds and their votes re-allocated to their rivals until one gets over 50%.
Cameron and the "No" camp argue however that the current system is simple, fair and effective, in that it allows voters to eject unpopular governments.
Opposition Labour leader Ed Miliband, who is backing the "Yes" campaign despite his party being split on the issue, added that it was a "once-in-a-generation opportunity" to change British politics.
But the stakes are highest for the Liberal Democrats, who have long campaigned for a change in the voting system which penalises small parties such as themselves.
Their popularity, and especially Clegg's, has plummeted over the past year as voters blame them for failing to stop the Conservatives from bringing in the harshest of the coalition's austerity measures.