Nigel Farage warned that half a million Islamist terrorists will travel to Britain under a proposed new EU migration and asylum policy.
The Ukip leader and MEP ditched his general election campaign temporarily to travel to Strasbourg to argue that it would be “wholly unacceptable” to introduce a new policy.
He cited warnings from the so-called Islamic State (also known as Isis or Isil) that it could send half a million jihadists to Europe through people-smuggling routes.
The proposals followed the death of as many as 900 illegal migrants, including young children, who drowned in the Mediterranean Sea off the coast of Libya earlier this month.
Following the tragedy, European Union leaders met to agree a four-point action plan to tackle the flood of migrants attempting the perilous crossing from Libya to Italy in the hope of claiming refugee status in the EU.
MEPs are now being asked to to approve conclusions by the European Council president Donald Tusk to prevent further tragedy but Farage is adamant that he will not support them.
He will claim that they amount to a "clear demand for the rapid implementation of a common EU migration and asylum policy”.
Farage will argue that Britain already has levels of immigration that are too high, and that opening the door to the resettlement of migrants arriving in Italy by boat would risk allowing in Islamist extremists who would "pose a direct threat to our civilisation".
Farage will say that the EU has "never failed to take advantage of a crisis" and claim that in this instance it is taking the opportunity of the migrant boat crisis to create a single immigration and asylum policy at a European level.
He will say that the prime minister must block the move or face the charge of finally and permanently giving away control of UK borders to Brussels.
Speaking in Hartlepool yesterday, Farage blamed the current crisis on British and French military intervention in support of the overthrow of Libyan dictator Muammar Gaddafi in 2011.
He said: "When people like me said it was mad, we were discounted.
"But it's now a completely failed state and has become a conduit for human trafficking and that, I think, could become, over the next 10 years, one of the biggest General Election issues.
"What do we do? Because if all these people come by their million to Italy and Greece and are given European passports they can come here too."
European Commission President Jean-Claude Juncker apparently wished Farage "good luck" in the upcoming South Thanet poll, because according to a tweet from Farage, he would not have to see him in the European Parliament again.
Meanwhile, Farage has also tried to claim that the Scottish National Party is “openly racist” towards English people.
Farage told BBC Radio 5 Live: “The biggest racism I've seen in British politics is happening north of the border with the SNP, where some of the anti-English hatred is reaching a truly astonishing level and I would think that if the BBC are worried about racism that's where they ought to be looking."