The Brexit campaign is the "great project" of liberalism and cosmopolitanism fighting against the cries of "more Europe" from Brussels, Boris Johnson has declared. The former mayor of London made the impassioned argument as he hit back at claims pro-leave politicians were "Little Englanders" and xenophobes.

"I am a child of Europe. I am a liberal cosmopolitan and my family is a genetic UN peacekeeping force," the top Conservative quipped.

"I can read novels in French and I can sing the Ode to joy in German, and if they keep accusing me of being a Little Englander, I will. Both as editor of the Spectator and Mayor of London I have promoted the teaching of modern European languages in our schools.

"I have dedicated much of my life to the study of the origins of our common European culture and civilisation in ancient Greece and Rome."

He added: "So I find it offensive, insulting, irrelevant and positively cretinous to be told – sometimes by people who can barely speak a foreign language – that I belong to a group of small-minded xenophobes.

"The truth is that Brexit is now the great project of European liberalism, and I am afraid that it is the European Union – for all the high ideals with which it began – that now represents the ancien regime.

"It is we who are speaking up for the people, and it is they who are defending an obscurantist and universalist system of government that is now well past its sell by date and which is ever more remote from ordinary voters."

Johnson's speech came just hours after David Cameron warned a Brexit could trigger conflict on the continent and channelled war leader Sir Winston Churchill to make his pro-EU pitch. "It wasn't through choice that we were alone. Churchill never wanted that," the prime minister said.

"Indeed he spent the months before the Battle of Britain began trying to keep our French allies in the war, and then after France fell, he spent the next 18 months persuading the United States to come to our aid."

But Johnson, a biographer of Churchill, questioned Cameron's sincerity. "Given that he was prepared only a few months ago to urge people to vote leave if they failed to get a substantially reformed EU, we have not got a substantially reformed EU, I think it's very, very curious that the prime minister is now calling this referendum and warning us that World War III is going to break out unless we vote remain," the Vote Leave spokesman argued.

"That is not the most powerful argument I've heard. Everybody knows that peace in Europe over the last 60 to 70 years has been guaranteed by Nato. What worries me now is it's the EU's pretentions to run a foreign policy and a defence policy that risks undermining Nato."

David Cameron says UK will keep peace in Europe by avoiding Brexit IBTimes UK