British prime minister David Cameron has warned that Britain leaving the European Union could provoke World War 3.

The United Kingdom is set to vote on whether or not to stay in the EU, and the debate is hotting up. Cameron says that Britain should stay in the EU to prevent World War 3 from breaking out.

British PM Says Brexit Could Lead To World War 3

British leader says Brexit could lead to World War 3

Cameron was on the referendum campaign trail and made a speech at the British Museum in London just hours before former London mayor Boris Johnson made his own speech calling for Brexit. Cameron chose to highlight Britain’s role in maintaining peace on the continent after being introduced by Labour ex-Foreign Secretary David Miliband.

“Can we be so sure peace and stability on our continent are assured beyond any shadow of doubt? Is that a risk worth taking?,” he said. “I would never be so rash to make that assumption.”

However Johnson later criticized Cameron’s speech, saying that “people should think very hard before they make these kinds of warnings.”

“No, I don’t believe that leaving the EU would cause World War 3 to break out on the European continent,” continued Johnson.

Former London mayor Johnson backs Leave campaign

A spokesman for Cameron later admitted that there were no contingency plans in place for a possible Leave vote, despite the warning that World War 3 could break out. Britain goes to the polls on June 23.

Cameron emphasized Britain’s historical role on the continent, referring to the nation’s involvement in “pivotal moments in European history: Blenheim, Trafalgar, Waterloo, our country’s heroism in the Great War and, most of all, our lone stand in 1940”.

He added: “What happens in our neighbourhood matters to Britain. That was true in 1914, 1940, 1989…. and it is true in 2016.”

He later evoked the memory of Winston Churchill, who “argued passionately for Western Europe to come together, to promote free trade and build institutions which would endure so our continent would never again see such bloodshed.”

World War 3 could be on the horizon in event of Out vote

Cameron claims that stability is threatened by a “newly belligerent Russia,” the Islamic State and a migration crisis.

“When terrorists are planning to kill and maim people on British streets, the closest possible security cooperation is far more important than sovereignty in its purest theoretical form,” he said, before claiming that “the terrorist threat against this country has grown” since he took office six years ago.

The Tory leader added: “Our threat level is now at severe, which means a terrorist attack is highly likely. Indeed, such an attack could happen at any time.”

Cameron said that Brexit would be “an abject act of national retreat.”

“Let’s not walkaway from institutions that helps us win the in the world,” he added.

Justice Secretary Michael Gove, who is a close personal friend of Cameron, had called for Britain to leave the Single Market if the country votes Out. The prime minister criticized Gove during his speech.

“I can only describe this as a reckless and irresponsible course,” he said. “These are people’s jobs and livelihoods.”

Former Labour Foreign Minister David Miliband introduced Conservative prime minister Cameron as party politics were put aside. At the same time ex-Chief of the Defence Staff, Field Marshal Lord Bramall, and three other war veterans recorded a video imploring pensioners to vote In.

“We would be going backwards in what we set out to cure after the terrible tragedies of the Second World War,” said 92-year-old Lord Bramall of a possible Brexit.

Ex-MI6 intelligence chief Sir John Sawers claimed that Brexit could leave Britain more vulnerable to terrorist attacks, a claim which Justice Secretary Michael Gove said was “flat wrong.”