EU Referendum Likely for U.K. as Conservatives Close in on Majority

The EU and the Union flags fly outside The European Commission Representation in the United Kingdom in central London January 23, 2013. Britain's Prime Minister David Cameron promised on Wednesday to give Britons a referendum choice on whether to stay in the European Union or leave if he wins an election in 2015, placing a question mark over Britain's membership for years. Stefan Wermuth/REUTERS

Britain must begin preparing itself for a referendum on its membership of the European Union, and the possibility of a Brexit, as the UK Conservative party look set to achieve a convincing, albeit surprising, victory in the 2015 general election.

In the run up to the election a key pledge from party leader and prime minister David Cameron, intended to placate Tory eurosceptics and dampen the impact of the UK Independence Party (Ukip), was that Britain would go to the polls in 2017 to decide on its continuing EU membership.

At the time of writing, the BBC is forecasting that the Conservatives will win 325 seats in total, increasing their share on the 2010 results by 19 - the first time an incumbent prime minister has done so in an election since Margaret Thatcher in 1983. Labour are forecast to win 239. The Conservative party could therefore form a stronger government than they did in 2010 when they formed a coalition with the Liberal Democrats.

While the Conservatives ran their campaign on the basis of being a safe pair of hands for the economy, and the business friendly option, the prospect of a Brexit could send serious jitters through the markets as Britain faces a potential future outside of the world's biggest trading bloc.

There have been warnings about the economic impact on the UK of a Brexit, with one thinktank Open Europe estimating it could cost the UK economy £56 billion a year. However, during his campaign trail Cameron claimed that business leaders were increasingly backing the idea of a referendum, but that they would want a vote held a year earlier to dispel uncertainty.

If the referendum goes ahead, David Cameron will most likely campaign to stay in the European Union, but will use the vote as leverage in hopes of winning major concessions to reform Britain's EU membership. It's likely that he will face considerable opposition from the the backbench right on the issue, who have long been pushing the Brexit agenda.

Cameron explained in an interview earlier this year that cabinet members in a future Conservative government would have to resign if they wanted to campaign to leave Europe, and that staying in a reformed EU is "good for Britain". However, the prime minister has also spoken about his desire to limit EU migration to the UK, and the importance of regaining control over areas such as welfare payments to migrants.

Boris Johnson, the London mayor who is now an MP after being parachuted into the safe seat of Uxbridge, says he is confident the referendum will happen.

"The PM has a clear mandate to deliver that, the Conservatives will emerge as the largest party and I think we should go ahead with this," he told the BBC. "The British people haven't had a vote on this in 40 years. It will be good not just for Britain but for the whole of Europe. There are plenty of people in Brussels waiting for Britain to take the lead on this."

The pro-EU Liberal Democrats have been almost wiped out in the election, with leader and deputy prime minister Nick Clegg defending his seat but seeing a number of key party figures who were in the previous government's cabinet losing out to Tory and Labour rivals. It is therefore unclear how much influence Clegg could now have over the next government, even if his party is included in some kind of deal - but he has previously refused to rule out agreeing to an EU referendum vote as part of a deal.

A referendum on the EU would have serious implications for the union in the UK. The Scottish National Party leader Nicola Sturgeon has said a vote to leave the EU could "justify" a second referendum on Scottish independence. The Scottish referendum last year saw the union narrowly survive, with 55% of Scots voting to stick with the UK, but the campaign ignited a Scottish nationalist election campaign which has seen the SNP projected to take 55 of Scotland's 58 seats in this general election.