With the latest poll giving the Leave camp a six-point lead, former Labour prime minister Gordon Brown pleaded the EU’s case to left-wing voters yesterday, while Irish Prime Minister Enda Kenny also began a tour of Britain to campaign against Brexit.

“Britain can’t build a relationship just on its own. Only the EU coming together can offer the economic incentives and strategic support so we can deal with the causes of terrorism,” Mr Brown said during a speech in Leicester, central England.

He insisted that the only way to defeat “gangmasters” fuelling ­illegal immigration was “through co-operation” with the EU.

Many Labour supporters plan to vote Leave on June 23 due to concerns over levels of immigration from the EU to Britain, leading to fears in the Remain camp that their votes could be ­decisive.

Britain’s most-read newspaper, The Sun, urged readers to back Brexit in an editorial splashed across its front page yesterday in the colours of the Union Jack.

“BeLEAVE in Britain” read the headline in a newspaper credited with generally backing the winning side and which famously claimed to have swung a general election in 1992.

A Guardian/ICM poll published on Monday gave Leave a 53 per cent to 47 per cent advantage, meaning that an average of the last six polls compiled by the WhatUKThinks website puts Leave ahead on 52 per cent.

Conservative Prime Minister David Cameron appeared to have temporarily stepped back from campaigning to allow Labour to make the case to its side.

Labour leader Jeremy Corbyn has made few appearances in the referendum campaign.

Mr Brown, who between 2007 and 2010 served as the party’s most recent prime minister, is seen as influential with Labour supporters.

His intervention late in the Scottish independence referendum campaign in 2014 was credited with helping the successful push to stay in Britain.

A group campaigning for Britain to leave the EU came under fire after tweeting that EU membership could lead to an “Orlando-style atrocity”. Home Secretary Theresa May, who wants Britain to stay in the EU, said the post was “utterly irresponsible”.

World stockmarkets slid after several opinion polls suggested the Leave camp could win.

Tokyo’s main stock index dived 3.5 per cent to a two-month low by the close early yesterday and slid further when it reopened. The pound hit two-month lows against both the euro and US dollar.

European Council president Donald Tusk warned that Brexit could spell the “destruction” of Western politics. “Do you know why these consequences are so dangerous? Because in the long term, they are completely unpredictable,” he told the German newspaper Bild. “As a historian, I am afraid this could in fact be the start of the process of the destruction of not only the EU but also of Western political civilisation.”

Mr Kenny’s tour of Britain is designed to shore up support for Remain among the estimated 600,000 Irish citizens living in Britain who can vote. “It is no secret that the Irish government very much wants the UK to stay as a member of the EU,” Mr Kenny said in Belfast, Northern Ireland.

“I very firmly believe that our common membership of the EU provided an important backdrop to the Irish and UK governments working together to secure peace in Northern Ireland.”

Ireland, an EU member, is concerned Brexit could hit its trade ties with Britain and mean the restoration of customs checks along its border with Northern Ireland.

AFP