Britain’s Work and Pensions Secretary says UK’s continued membership in the European Union (EU) will make it more vulnerable to terrorist attacks.

Iain Duncan Smith told the state-run BBC on Sunday that being a member of the bloc "leaves the door open" to terrorist attacks such as the one in the French capital last November.

Duncan Smith suggested refugees arriving in the EU could eventually end up in the UK without proper consideration of their motivations.

"This open border does not allow us to check and control people that may come and spend time," he said.

"We've seen what happened in Paris where they spent ages planning and plotting so who's to say it's not beyond the wit of man that those might already be thinking about that."

The senior official's comments contradict Prime Minister David Cameron, who says the UK is "safer and stronger" in the EU.

The PM says the UK's future is in a "reformed" European Union.

He has also warned that leaving the EU would give the UK an "illusion of sovereignty" but not full control.

The stream of refugees has triggered the worst such crisis Europe has seen in decades.

Most of the refugees are from war-ravaged and poverty-stricken countries in the Middle East and Africa, with many saying EU powers are also to blame for the unprecedented exodus as they have done little to contain the problems in those regions.