Britain will vote on whether to remain in the EU on Thursday 23 June, Prime Minister David Cameron has said.
The prime minister made his historic announcement in Downing Street after briefing the cabinet.
He said he would be campaigning to remain in a reformed EU – and described the vote as one of the biggest decisions «in our lifetimes».
Ministers immediately divided up into the leave and remain camps as the campaigns got under way in earnest.
- The UK’s EU vote: All you need to know
- High stakes and missed meals – how the EU summit unfolded
- Nick Robinson: Why EU vote is about you
- Katya Adler: A hard-headed calculation to avoid Brexit
Home Secretary Theresa May heads the list of those who have announced they will campaign to stay – but Justice Secretary Michael Gove has signed up to the leave campaign.
Leave campaigners are also hoping London Mayor Boris Johnson will join their cause – but he has yet to declare where he stands.
‘Source of instability’
In his statement, Mr Cameron warned that leaving the European Union would be a «leap in the dark» as he urged voters to back his reform deal.
«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 direct appeal to voters, 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.»
Mrs May said the EU was far from perfect but «for reasons of security, protection against crime and terrorism, trade with Europe, and access to markets around the world» it was in the national interest to remain in.
Mr Gove said it had been the most difficult decision of his career to go against the prime minister but he believed «our country would be freer, fairer and better off outside the EU», adding that «far from providing security in an uncertain world, the EU’s policies have become a source of instability and insecurity».
Other ministers to declare they will campaign to remain, following Mr Cameron’s statement, were Business Secretary Sajid Javid – previously seen as a potential outer – International Development Secretary Justine Greening and Transport Secretary Patrick McLoughlin.
Commons leader Chris Grayling, Culture Secretary John Whittingdale, Work and Pensions Secretary Iain Duncan Smith, Northern Ireland Secretary Theresa Villiers and employment minster Priti Patel, who is not a full cabinet member but attends meetings, have all joined the leave campaign.
Energy minister Andrea Leadsom – who is not a member of the cabinet – will also back the leave campaign.
Mr Cameron claims his EU reform deal – hammered out at a two-day summit in Brussels – will give the Britain «special status» within the bloc – tackling concerns over migrants getting «something for nothing» from the benefit system and exempting the country from the EU drive for «ever closer union».
But critics say it does nothing to tackle high levels of immigration or take back powers from Brussels, with UKIP leader Nigel Farage branding it «truly pathetic».
Alan Johnson, chair of Labour In for Britain, said the party would be «united in making the case that Britain is better off in Europe».
«Our EU membership brings Britain jobs, investment, trade and keeps us safe. Leaving the EU would put all that at risk and diminish Britain’s influence in the world. It was pressure from Labour that meant David Cameron has been prevented from trading away rights at work in this deal and we can now get on with our campaign to keep Britain in Europe.»