Nigel Farage will say today that allowing refugees into Europe ‘could lead to half a million Islamic extremists coming to our countries and posing a direct threat to our civilisation’.

The Ukip leader will say the boatloads of people trying to get to the continent from North Africa could provide a cover for jihadis wanting to do harm.

Mr Farage will make his comments in a debate at the European Parliament in Strasbourg in the wake of more than 1,000 migrants drowning in the Mediterranean.

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Warning: The Ukip leader will say the boatloads of people trying to get to the continent from North Africa could provide a cover for jihadis

He will warn that if the EU agrees to give refuge to migrants from North Africa, it could lead to millions being given passports that allow them to move to Britain.

A source close to Mr Farage said he was taking time out from the campaign trail in Britain to focus the election debate on immigration.

Campaign bosses believe a provocative intervention could have the same effect as his controversial remarks on foreigners with HIV being treated in Britain – which were part of a so-called ‘shock and awful’ strategy to get attention and appeal to the party’s ‘core voters’.

Mr Farage thinks his party could still get more than ten MPs if he manages to cause a ‘big shock’ in the eight days before polling day.

A senior Ukip aide said: ‘He needs to make a special intervention. This is a big moment in the campaign.

‘Cameron and Miliband do not want to talk about this because they know the whole issue hinges on EU membership.

‘Nigel is going to highlight how jihadis are entering Europe, getting EU passports, and then are able to easily come to Britain because of the open-borders policy.

'If there is going to be one country where these guys are going to head to, it is going to be us because of the Iraq war and our involvement in Afghanistan and against Islamic State.’

Mr Farage said yesterday he opposed EU action to tackle migrant deaths in the Mediterranean because it could lead to a common migration policy and let millions of people into Britain. He added that the problem had the potential to be more damaging than the eurozone crisis.

Mr Farage will warn that if the EU agrees to give refuge to migrants from North Africa, it could lead to millions being given passports that allow them to move to Britain

‘I think what is happening in Strasbourg is far more significant than anything that has been said by any of the party leaders about immigration … during this campaign,’ he said.

‘They utterly refuse to accept that we are no longer in control of our borders … ‘I’m quite certain Miliband and Cameron will try and ignore this, so I am going there [Strasbourg] to engage in that debate and make sure they cannot ignore it.’

He added: ‘Are we about to see one of the great Brussels dreams come true … a common EU immigration policy? We currently have a net migration figure of 300,000. Goodness knows what it could be if this happens.

'Potentially EU passports are about to be given to a very large number of people and the British political class in Westminster is powerless.’