Lord Paddy Ashdown has urged UK voters to be proud of their "mongrel nation," in a bid to counter the anti-immigration warnings from Brexit campaigners in the EU referendum campaign. The former Liberal Democrat leader, addressing a small audience at the RAF Club in London's Mayfair on 10 June, claimed that breaking away from Brussels would not help Britain address the issue.

"We seem to act nowadays as if immigration is a new challenge, it's not... [Sir Winston] Churchill called us a mongrel nation, made up as we are of Saxons, Danes and Vikings, Huguenots, Jews, West Indians and a new wave of European workers from Eastern Europe," the peer declared.

"That is what has shaped our national character and, by the way, London is the mongrel city, which is one of the reasons why it is the world's only successful mega international city."

He added: "Migration is not a new fact, it is an age old one and it's not going to go away. Mass movements of people is the new norm, the new global strategic challenge of our time. This is an issue which cannot be tackled by individual nations acting alone, it can only be tackled regionally and globally."

Ashdown also warned that a Brexit could see French-style migrant camps appearing 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."

The comments come after Vote Leave, the official Brexit campaign, announced that they supported an Australian-style points system to reduce the UK's immigration levels. The group, supported by Boris Johnson and Justice Secretary Michael Gove, made the move after the Office for National Statistics (ONS) revealed that net migration to the UK had climbed to 333,000 in 2015 – three times more than David Cameron's "tens of thousands" pledge.

Ashdown also attacked Brexit campaigners' claims that a Leave vote on 23 June would help restore the UK's sovereignty. The Liberal Democrat peer claimed this definition of sovereignty was severely outdated.

"For a medium sized nation like Britain, standing alone does not give us more control, it makes us more vulnerable to global forces. It hands the control that we enjoy – by pooling sovereignty with our friends – over to the global forces to which we would be more nakedly exposed. Pooling sovereignty with our friends does not diminish British sovereignty, it is increases it."

Ashdown's speech comes with less than two weeks to go before the EU referendum, with some recent opinion polls putting the campaigns near neck-and-neck. The latest online survey 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.

Lord Paddy Ashdown, Lib Dem peer
Lord Paddy Ashdown, former Liberal Democrat leader Reuters