Former prime minister Sir John Major has accused the Brexit campaign of "offensive" tactics and dismissed arguments about the powers handed to Brussels by claiming that North Korea was the only nation with "undiluted sovereignty" because of its international isolation.
The ex-Conservative leader, who is campaigning for the UK to remain in the European Union, warned there would be economic and political damage if the country votes to leave in the referendum on June 23.
He rejected the claims about patriotism made by some in the Brexit camp, suggesting that their approach of "splendid isolation" would leave the country weaker.
"Day after day you have had the Brexit people producing soundbites that are either offensive or inaccurate or just plain silly," Sir John said.
"I don't believe that it is patriotic to argue for a case that is going to make this country weaker and is going to make the wellbeing of this country less certain in the future."
He told BBC Radio 4's Today programme: "I'm no starry-eyed Europhile, but I have no doubt where our future lies.
"The EU helped free Spain, Portugal and Greece from fascism. It helped rebuild the Balkans after war.
"It offered a new future to countries once imprisoned within the Soviet empire, and across Europe old enemies, who for centuries fought against each other, now live and work beside each other.
"It has increased our prosperity. Once the sick man of Europe, we are now on course to be the biggest economy in Europe."
He warned: "If we go it alone we will lose free trade agreements with over 50 countries. It would take many years to renegotiate them all and we would never get as good a deal as we now have as part of Europe.
"Before us all is a fateful choice: if we leave Europe, both Europe and the UK would be weakened.
"Our relationship with America would wither - America needs an ally inside the European Union and it could no longer be us.
"At home, Scotland may choose to leave the UK."
He accused the Brexit camp of using "nonsense" rhetoric about the influence of the EU, saying: "To listen to them you would think we are entrapped in the clutches of an evil empire, not in a democratic partnership with our European neighbours whose sunshine and pavement cafes we enjoy during holiday breaks."
He added: "Painting Britain as a victim of Europe is simply ludicrous. We gain more than we give, we win more than we lose."
The Leave campaign has said that Brexit would restore sovereignty to the UK, freeing it from the influence of Brussels and the European Court.
But Sir John said: "If you want undiluted sovereignty in the modern age, when everybody is interconnected, then go to North Korea because that is where you will get it.
"It is certainly true that we share sovereignty. We take some sovereignty from other people, we share some of ours.
"We haven't surrendered it because at the end of the day the House of Commons, our representatives, can say 'we won't have this, we will leave the European Union'.
"But in the modern world, the modern world of interconnectivity, the modern world with the economy that now exists, you have to share sovereignty or you find yourself isolated and weaker."
Responding to the "North Korea" comment, Brexit-supporting Conservative minister George Eustice said: "What we really want is more control over our affairs, we don't want European courts telling us what to do, second-guessing the decisions of ministers.
"I don't accept that caricature put forward by John Major. There are lots of other independent countries in the world - the United States, Australia, New Zealand.
"They are not in the European Union, they do not have to put up with the sort of nonsense we have to put up with, being told what to do by European courts and having their decisions second-guessed.
"There are many examples of successful, independent countries in the world who are not isolationist and the UK would never, ever be an isolationist country."
The Farming Minister told Today: "If you look at John Major's time in government, the achievements he is proudest of are where he secured opt-outs from the European Union and his greatest disasters were where he opted in to things.
"The ERM (Exchange Rate Mechanism) was a catastrophic economic decision, I was in our family business at the time, it was disastrous for the country, it caused huge unemployment, many businesses went bust.
"But the bits he is proudest of are the opt-out from the euro, the opt-out from Schengen.
"We ought to ask ourselves, if every opt-out we got works and we have delivered better policy outcomes, surely we could do better if we took back control of more areas?"