With the flow of refugees and migrants into Europe growing, Britain should vote for Brexit in the upcoming referendum, not to let Islamic State (IS, formerly ISIS/ISIL) terrorists filter into the UK, said Tory MP Liam Fox, a former Defence Secretary.

Jihadists could be entering the country among asylum-seekers, refugees or migrants, Fox told the Telegraph, adding that current migration crisis poses a threat "much worse" than recent sexual and other crimes in Germany's Cologne.

READ MORE: UK risks Cologne-style attacks by remaining in EU, Brexit campaigners claim

Southern European countries, through which people arrive from the Middle East, "have no idea whether these people are genuine refugees or asylum seekers, or economic migrants, or terrorists operating under the cover of either," Fox said.

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If Britain remains an EU member, those people "will have an absolute right to come to the UK - and we won't know who they are either," Fox added, saying that they might be crossing the borders both to work, or "coming to do us harm."

"In a world where you've got ISIL out there, you cannot afford to assume that there is no risk," the pro-Brexit politician said, claiming that by regaining its "sovereignty" in the referendum, UK will be able to protect its own borders.

Criticizing David Cameron's and other pro-European campaigners for their claims that being in the bloc is "essential" for UK's security, Fox said such statements were "beyond belief," and EU with its "weakness" should be rather regarded as "a risk to our security."

A week ago, Liam Fox, along with UKIP leader Nigel Farage and Labour MP Kate Hoey launched a cross-party Brexit platform, 'Grassroots Out,' campaigning for the UK to leave the EU. The bloc's migration policy of open doors is among the main arguments in favor of a British exit, politicians campaigning for it, say.

Earlier this week, there have been reports that Britain will be offered an "emergency brake" rule to help lower the rate of immigration from EU countries. According to the deal, offered by the EU, UK and other EU governments will be allowed to deny migrant workers the right to benefits for up to four years, Reuters reported.