DAVID Cameron yesterday embarked on the biggest political gamble by a British Prime Minister in 40 years, as he confirmed the In-Out referendum on Europe would be on June 23.

Backed into the move by the rise of Ukip and right-wing Tory MPs, Cameron announced the historic vote in Downing Street after a two-hour meeting of his divided cabinet. The move will put the issue of Europe front and centre during the campaign for Holyrood 2016.

The Prime Minister said the decision on whether the UK should remain in the European Union, a choice last made by voters in 1975, would be one of the biggest “in our lifetimes”.

Re-deploying many of the arguments from the independence referendum, he said the UK would be safer staying in a reformed EU, while Brexit would be a “leap in the dark”.

He said the “special status” he had secured for the UK meant it could enjoy the benefits of the EU in terms of trade and security, without having to sign up to a European superstate.

He said: “The choice is in your hands - but my recommendation is clear. I believe that Britain will be safer, stronger and better off by remaining in a reformed European Union.

“Those who want to leave Europe cannot tell you if British businesses would be able to access Europe’s free trade single market, or if working people’s jobs are safe, or how much prices would rise. All they’re offering is a risk at a time of uncertainty - a leap in the dark.”

In a day of fast-moving developments, the reforms on which Cameron expended so much energy at last week’s European Council were overshadowed by more fundamental arguments about uncertainty and sovereignty.

Freed from collective responsibility, five Cabinet ministers went to the headquarters of the Vote Leave campaign to pose for photos with a “Let’s take back control" poster.

Led by Justice Secretary Michael Gove, the group included Work and Pensions Secretary Iain Duncan Smith, Commons Leader Chris Grayling, Culture Secretary John Whittingdale, and the Northern Ireland Secretary Theresa Villiers.

Employment minister Priti Patel, who attends Cabinet, was also part of the Out group, earning it the nickname the Gang of Six.

However Cameron was backed by his Eurosceptic Home Secretary Theresa May and Foreign Secretary Philip Hammond, as well as by the wavering Business Secretary Sajid Javid.

London Mayor Boris Johnson, who is being desperately wooed by the Out campaign, is expected to make his position known today on the BBC’s Andrew Marr show.

Gove, one of Cameron’s closest allies, said it had been the most difficult decision of his political life to oppose Cameron's position.

"My instinct is to support him through good times and bad. But I cannot duck the choice which the Prime Minister has given every one of us," he said.

"I believe our country would be freer, fairer and better off outside the EU. If, at this moment of decision, I didn't say what I believe I would not be true to my convictions or my country."

Grayling commended Cameron on his “Herculean effort” to secure change in Brussels, but added: “I actually believe the EU is holding this country back. We cannot control our borders, limit the number of people who come here do trade deals. I do not believe we can take decisions in the national interest when we are part of the European Union.”

Theresa May said the EU was far from perfect but needed “for reasons of security, protection against crime and terrorism, trade with Europe, and access to markets around the world”.

Labour leader Jeremy Corbyn said the recent negotiations were a "missed opportunity" but confirmed: “We will be campaigning to keep Britain in Europe regardless of David Cameron's tinkering because it brings investment, jobs and protection for British workers and consumers.”

Ukip leader Nigel Farage, for whom June 23 will also be a make-or-break moment, said: “The 23rd is our golden opportunity, let battle be joined. Mr Cameron keeps on telling us that Britain would be better in a 'reformed Europe'. But he fails to point out that there is no reformed European Union on offer here. The Prime Minister's EU deal is pathetic. We have the prospect of a free, secure prosperous and exciting future outside of the EU."

Former Scottish and Foreign Secretary Sir Malcolm Rifkind said there would be “dancing in the Kremlin” if the UK left the EU and the latter “started to disintegrate”.

The official In campaign will probably be led by Britain Stronger in Europe, while the Out side will be led by Grassroots Out or Vote Leave, after the withdrawal of the Leave.Eu group.

Giving a hint of the bloody fight to come, Britain Stronger in Europe yesterday released a campaign video accusing leave campaigners of "utter hypocrisy" for attacking Cameron's deal, claiming that many of them demanded the same reforms in the past.