UK former defense secretary Liam Fox said Sunday the "threat from the migration crisis could be much worse than the sex attacks in Cologne".

In an interview with the Telegraph, he warned that "terrorists could enter Britain posing as refugees."

The former defense secretary urged voters to reclaim Britain's "sovereignty" in the EU referendum, in order to protect the border as the European migration crisis grows.

In the strongest attack from a senior Tory so far on the Prime Minister's pro-Europe campaign, Fox told the Telegraph it was "beyond ridiculous" for David Cameron to claim that EU membership improved national security.

He said Europe posed many threats to the UK, from the economic turmoil in the Eurozone to a repeat of the scenes in which gangs of migrants assaulted women in Cologne on New Year's Eve.

"It could even be worse, with terrorists entering Britain among the crowds of refugees in future," he said.

Fox's comments came after a Labour MP said the mass assault by migrant gangs in the German city were comparable to the treatment of women in Birmingham every weekend.

Fox warned that the influx of migrants into the EU posed a major threat to Britain's security.

Southern European countries such as Greece and Italy "have no idea who these people are" who have arrived in boats from across the Mediterranean Sea, he said.

"A million last year, maybe two million this year - they 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.

"If we remain in the European Union, if these people are naturalized in any other European country, they will have an absolute right to come to the UK. And we won't know who they are either," he added.

"In a world where you've got Daesh out there, you cannot afford to assume that there is no risk," Fox said.

Source: MENA