LONDON (AFP) - With one month to go until Britain's EU referendum, the Remain campaign is pulling ahead amid warnings over the international consequences of a Brexit and increasingly outlandish claims at home.
The battle for votes ahead of the June 23 referendum has drawn in US President Barack Obama, EU leaders and the IMF, prompted comparisons between the European Union and Adolf Hitler and sparked a warning about the risk of World War III.
Prime Minister David Cameron is leading the campaign to "Remain", backed by leaders such as Obama amid international unease at the prospect of Britain becoming the first EU member ever to leave the bloc.
The International Monetary Fund has warned of a potentially severe global market reaction to a vote to a "Leave" vote, while G7 finance ministers this weekend warned of the prospect of a Brexit "shock".
The European Commission said the uncertainty is already affecting growth in the eurozone, while the Bank of England made a similar point regarding the British economy.
Opinion polls suggest that, barring a major upset, "Remain" is on course to win.
An average of the last six surveys by the What UK Thinks research project gives the campaign a 10-point lead over the "Leave" camp, on 55 per cent, excluding undecideds.
Bookmakers have also put their money on Britain staying in, with William Hill and Ladbrokes offering odds that imply a Remain vote is more than 85 per cent likely.
Experts caution that turnout will be key, with many of those most supportive of the EU - young people and ethnic minorities - also least likely to vote.
But the polls will offer hope to Cameron, who many expect would be forced to resign if he loses, with leading Brexit supporter Boris Johnson, the former London mayor, among those waiting in the wings.
They also reduce the likelihood of a second referendum on Scottish independence, after the governing nationalists warned a Brexit could see the broadly pro-European Scots make another bid to leave the UK within two years.
Cameron called the referendum in 2013 to placate eurosceptics in his Conservative Party, but senior figures have turned against each other in an increasingly shrill campaign.
Johnson, tipped as a possible future Conservative leader, has been canvassing in towns across Britain, calling on voters to "take back control" from Brussels.
He has been making headline-grabbing, if questionable, claims about the over-reaching power of the EU, including that it bans the sale of large bunches of bananas and does not allow tea bags to be recycled.
More seriously, Johnson caused outrage by suggesting in a newspaper interview that the EU had similar ambitions to Hitler in unifying Europe under one authority.
Cameron has also been criss-crossing the country addressing audiences in businesses and factories, giving stark warnings of the risks of going it alone.
He was accused of suggesting that a new world war could break out after warning that a Brexit would threaten decades of peace in Europe.
The prime minister also said that the leader of the Islamic State extremist group, Abu Bakr al-Baghdadi, would welcome Britain leaving the bloc.
Paul Taggart, politics professor at Sussex University, said campaigners were trying to simplify complex issues and "it's about finding mantras that work".
But the tone of the debate, which has seen senior Conservatives accuse each other of smears, of being "reckless" and "economically illiterate", has sparked concerns about the unity of the party after June 23.
The first television debate will involve Cameron and UK Independence Party leader Nigel Farage on June 7, although they will not go head to head, instead taking questions one after the other from a live studio audience.
The anti-immigration UKIP has made the prospect of ending mass EU immigration a central theme of the "Leave" campaign.
A new ComRes poll this week put the economy as the top concern of voters, followed closely by immigration.
Farage has warned that if people feel they have lost control, including of their borders, "then violence is the next step".