SKY•REUTERS Farage will try to refocus the Leave campaign on the threat to Britain’s borders from EU migrants

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At a high profile event in London the UKIP leader weighed into the Brexit debate saying: “Theresa May says its difficult to control immigration as part of the EU. She’s wrong – it’s not difficult, it’s impossible.” Farage went on to warn that the drive to quit the EU would fail unless campaigners do more to highlight the threat of mass immigration. In an outspoken intervention in the referendum debate, the Ukip leader accused the Vote Leave campaign of putting too much effort into reacting to Government scaremongering rather than stressing the dangers of staying linked to Brussels. And insisted that border control is the key issue that can win over voters.

“If we are to leave the EU this issue must be at the front and centre of the Brexit campaign,” Mr Farage said. “The only way we can control immigration is by leaving the EU.” His intervention, with a speech in central London, is the first sign of nervousness about the strategy of the Leave camp since the official start of the referendum campaign. It came as an opinion poll yesterday showed that the Ukip leader is now more trusted by voters on the EU issue than Prime Minister David Cameron.

GETTY The 52-year-old is expected to launch scathing attack on German chancellor Angela Merkel

In a speech in London this morning Mr Farage highlighted the threat of another mass migration surge if Turkey and a string of Balkan nations are given EU membership. He launched an attack on the EU over the migrant crisis and savage German chancellor Angela Merkel for inviting tens of thousands of asylum seekers into her country.

“We should not have to pay for the EU’s and Mrs Merkel’s errors,” he said. Mr Farage warned that migrants responsible for mass sex attacks in Germany on New Year’s Eve could get the right to come to Britain. And added Europe’s open borders have given jihadist terrorists freedom to roam around the EU and target Britain. The opinion poll by YouGov showed that 23 per cent of voters said they trusted the Ukip leader on the EU, with only 20 per cent now believing the Prime Minister.

GETTY Farage believes Europe's open borders have allowed jihadis to roam freely between countries

GETTY Polls show the public are now more likely to trust Farage than Cameron