The campaign for Britain to leave or stay part of the European Union is already in full swing ahead of a membership referendum planned for June 23. Here are some of the key players in the debate:
The "Remain" camp:
-- Prime Minister David Cameron will lead the campaign for Britain to stay in the European Union. Most MPs from his Conservative party will fall into line, although a group of eurosceptics will vote against.
-- Jeremy Corbyn: The main opposition Labour party has said it will campaign to stay, although a few eurosceptics there too will decide to vote against.
Corbyn has branded Cameron's EU deal a "sideshow" but has said he will campaign to stay because of investments, jobs and worker protection from the EU.
-- Nicola Sturgeon: Scotland's first minister and the head of the pro-independence Scottish National Party has said she will be at the "forefront" of efforts to stay in, amid warnings that a "Brexit" could trigger a second vote for Scotland to leave the United Kingdom.
-- Campaign: "Britain Stronger in Europe" is the main group advocating British membership. It is led by Stuart Rose, a former chairman of the retailer Marks & Spencer and a Conservative member of the House of Lords, but has kept a low profile so far.
-- Business: Key business leaders including Richard Branson have spoken out for EU membership, with the Virgin founder warning a departure would be a "very sad day". Barclays bank chairman John McFarlane has warned the City of London, Europe's premier financial hub, would be "significantly" worse off without the EU.
-- Celebrities: Several cultural figures have come out as pro-EU. The latest, award-winning British actress and campaigner Emma Thompson, said leaving Europe would be "a crazy idea". "Of course I'm going to vote to stay in Europe. Oh my God, it would be madness not to," she told reporters at the Berlin Film Festival.
-- Royals: Prince William never actually mentioned the word Europe but in a speech at the foreign ministry in London this month, the second in line to the throne made some comments that were widely interpreted in British media as being in favour. "Our ability to unite in common action with other nations is essential, it is the bedrock of our security and prosperity," the prince said.
-- Ministers: Five of the cabinet's 22 members have so far come out in favour of Brexit: justice minister Michael Gove, work and pensions minister Iain Duncan Smith, Northern Ireland minister Theresa Villiers, sports and media minister John Whittingdale and Chris Grayling, the cabinet's representative in parliament.
-- Nigel Farage: The head of the anti-EU UK Independence Party (UKIP), who is a member of the European Parliament but failed to get elected to the British parliament last year, has advocated for Britain to leave the EU all of his political life. On Saturday, Farage tweeted: "June 23rd: our golden opportunity. Let battle be joined. We want our country back". He said life outside of Europe would mean "control of our borders, global trade deals, making our own laws. An exciting future".
-- Campaign: Various movements have been set up to advocate Brexit from both the right and the left - among them "Vote Leave", "Labour Leave", "Leave.EU". They have been quick off the starting blocks in the campaign but relations between them have sometimes been AFP
-- Business: Some entrepreneurs have spoke out for Brexit, including vacuum cleaner tycoon James Dyson. The inventor was quoted by the Daily Express as saying that he did not want to stay in a Europe "dominated and bullied" by Germany.
-- Celebrities: Only very few cultural figures have declared public support for Brexit. Oscar-winning actor Michael Caine has said Britain should leave if it does not manage to negotiate "extremely significant changes". "I sort of feel certain we should come out," the 82-year-old told BBC radio.