By Elizabeth Piper and Estelle Shirbon
LONDON, June 23 (Reuters) - Britons were voting on Thursday on whether to stay in the European Union in a referendum that has split the nation and is being nervously watched by financial markets and politicians across the world.
An Ipsos MORI poll for the Evening Standard newspaper, conducted on Tuesday and Wednesday, suggested support for "Remain" stood at 52 percent while "Leave" was on 48 percent.
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British Prime Minister David Cameron (L) poses for a photograph after addressing pro-EU "Vote Remain" supporters at rally in Bristol June 22, 2016. REUTERS/Geoff Caddick/Pool[/caption]
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Scottish Conservative leader Ruth Davidson and Mayor of London Sadiq Khan speak during The Great Debate on BBC One, on the EU Referendum in London, Britain June 21, 2016. REUTERS/Stefan Rousseau/Pool[/caption]
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Britain's Prime Minister David Cameron speaks about the EU referendum outside 10 Downing Street in London, June 21, 2016. REUTERS/Stefan Wermuth[/caption]
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A woman reads a newspaper on the underground in London with a 'vote remain' advert for the BREXIT referendum, Britain June 22, 2016. REUTERS/Russell Boyce[/caption]
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People hold signs in Trafalgar Square during a 'Yes to Europe' rally for young people, ahead of Thursday's EU referendum, in central London, Britain June 21, 2016. REUTERS/Dylan Martinez[/caption]
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A polling station sign is seen, ahead of Thursday's EU referendum, in central London, Britain June 21, 2016. REUTERS/Stefan Wermuth[/caption]
A truck is driven by Vote Leave supporters through Parliament Square, ahead of Thursday's EU referendum, in London, Britain June 21, 2016. REUTERS/Stefan Wermuth[/caption]
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A truck is driven by Vote Leave supporters through Parliament Square, ahead of Thursday's EU referendum, in London, Britain June 21, 2016. REUTERS/Stefan Wermuth[/caption]
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A polling station sign for the Referendum on the European Union is erected by in the village of St Florence, Near Tenby, Pembrokeshire in Wales, Britain, June 23, 2016. REUTERS/Rebecca Naden[/caption]
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Ballot papers wait to be used at a polling station for the Referendum on the European Union in north London, Britain, June 23, 2016. REUTERS/Neil Hall[/caption]
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Electoral workers carry signs as they prepare a polling station for the Referendum on the European Union in north London, Britain, June 23, 2016. REUTERS/Neil Hall[/caption]
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Scotland's First Minister Nicola Sturgeon leaves after voting in the EU referendum, at Broomhouse Community Hall in Glasgow, Scotland, Britain June 23, 2016. REUTERS/Clodagh Kilcoyne[/caption]
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People arrive to vote at a polling station for the Referendum on the European Union in Heald Green, Stockport, Britain, June 23, 2016. REUTERS/Andrew Yates[/caption]
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A woman carries an umbrella past a pub being used as a polling station for the Referendum on the European Union in west London, Britain, June 23, 2016. REUTERS/Toby Melville[/caption]
Sterling gained 1.5 percent against the dollar on Thursday, breaking above $1.49 for the first time since December 2015 after the Ipsos MORI poll was released.
The likelihood of a "Remain" vote implied by Betfair betting odds stood at 86 percent, the firm said shortly after the poll.
Finance leaders from Group of Seven leading economies will issue a statement stressing their readiness to take all necessary steps to calm markets if Britain votes to leave, government officials with direct knowledge of the matter said.
Britain's AAA credit rating could be swiftly downgraded by Standard and Poor’s if the Brexit camp prevails, S&P chief sovereign ratings officer Moritz Kraemer told German daily newspaper Bild.
On Wednesday, campaigners from both sides tried to win over the estimated 10 percent of the 46.5 million electorate who polls suggest had still not decided which way to vote.
The "In" campaign took aim at their rivals by saying a Brexit would hurt the economy, security and the country's status. The "Out" campaign said high levels of immigration could not be controlled inside the EU and it was time to bring powers back from Brussels to London.
SPLIT NATION
The killing of Cox, a 41-year-old mother of two young children, in her electoral district in northern England prompted a pause in the campaign and soul-searching about its tone. Cox's husband said she had been concerned about the coarsening of political dialogue.
The man charged with her murder, asked to confirm his name in a London court, responded: "My name is death to traitors, freedom for Britain".
Britain is deeply divided on EU membership, with big differences between older and younger voters, and between pro-EU London and Scotland and eurosceptic middle England.
That split was reflected in British newspapers' front pages. "Independence Day" was the front page headline of the Sun tabloid, Britain's biggest-selling newspaper, while the Daily Mirror warned "Don't take a leap into the dark".
The issue also dominated news bulletins far beyond Britain. In China, the Global Times, published by the ruling Communist Party's official People's Daily, warned Britain would lose its influence globally if voters backed Brexit.
Whatever the outcome of the vote, the focus on immigration to Britain, which has increased significantly in recent years, could worsen frictions in a country where the gap between rich and poor has also been widening.
If Britons choose to leave, Scottish leader Nicola Sturgeon has suggested Scotland may call a referendum on leaving the United Kingdom.
Even with a vote to stay, Cameron could struggle to repair the rifts in his party and hold on to his job.
Foreign leaders, from U.S. President Barack Obama to Chinese leader Xi Jinping, have called on Britain to remain in the EU, a message supported by global financial organisations, many company bosses and central bankers.
International banks have warned that the value of the pound could fall dramatically if Britain votes to leave and traders expect markets to be more volatile than at any time since the 2008-09 financial crisis.
The "Out" campaign says a fall in the value of the pound would boost exports and has found support among some financial specialists and small businesses. It has urged voters to ignore what it calls the "establishment" which it says has the most to lose from Brexit.
The EU has struggled with migration and economic crises and a Brexit vote would boost opposition to it within other member states.
"Stay with us," European Council President Donald Tusk told British voters on Monday.
"Without you, not only Europe, but the whole Western community will become weaker. Together, we will be able to cope with increasingly difficult challenges of the future."