The "higher water of federalism" continues to rise inside the EU and a Remain vote at the referendum would see the UK locked into a "bureaucratic night", according to Iain Duncan Smith. The former work and pensions secretary issued the warning with under two weeks to go before the 23 June vote, arguing that the EU's structure is designed towards more federalism.

"We are facing a decision as to whether or not we want to be tugged along reluctantly behind an EU running on a course on which many of them believe is the right thing, which is the eradication of the competing nation state and creation of a supranational federal union," the Vote Leave spokesman declared.

"For many it is a strong belief, I don't share it and I don't believe the British people share it either, but I would rather us vote to Leave and no longer be that country that spends its time arguing and getting angry and being the awkward one that eventually, after the argument, gets tugged along in that direction even though we've already complained about it.

"It would be far better for us to leave and have a much better relationship with our friends and compatriots in the EU and beyond the EU."

Duncan Smith cited Altiero Spinelli, the Italian political theorist and federalist credited as the architect behind the EU. "I must say that the water has carried on ever since [The Maastricht Treaty] and it continues to rise because that is what the structure Spinelli and his team put together," the senior Conservative MP claimed.

"I love Europe, I'm a European," he concluded. "It's a wonderful continent, it's brilliant in many regards, possibly the most brilliant continent in the world. So I'm very keen to be part of that continent. I don't think we are leaving Europe, we are leaving the EU."

Duncan Smith also said a Brexit would send a message to other 27 nations in the EU that it is "really time to change". The speech, part of the UK in a Changing Europe's annual conference in Westminster, came hours after Lord Paddy Ashdown warned against a Leave vote at the referendum.

The Liberal Democrat peer claimed that French-style migrant camps could appear in the south of England. "Even the UK cannot avoid the effects of mass migration by ducking out of Europe, as we shall discover painfully and directly if we do vote Brexit and Calais, with its barbed wire, its police controls and its squalid human camps moves to Dover," Ashdown said.

The interventions comes as the EU referendum campaign ramps up. The latest online opinion poll from YouGov, of more than 2,000 people between 5 and 6 May, put Remain on 43% and Leave on 42%, with 11% of respondents undecided.

Iain Duncan Smith
Iain Duncan Smith, Vote Leave spokesman Getty