There's no EU support for the one thing that could stop a Brexit - a curb on immigration

Britain is on the cusp of leaving the European Union - dubbed a Brexit - because there seems to be absolutely no wriggle room for the country to curb immigration levels.

Prime Minister David Cameron promised Britons that his government would push for a "better deal" with the EU, which includes renegotiating immigration rules for people coming to the UK, ahead of the 2017 referendum.

Various polls over the last year have shown how the Freedom of Movement Act, which allows all EU citizens to easily migrate to any other member state, as well as immigration in general is one of the factors that pushes Uk voters to pip for exiting the 28 nation block.

However, European Council President Donald Tusk said on Monday that while there is a "strong will" among EU states to renegotiate the terms of Britain's membership, there was absolutely no consensus over the UK having stricter immigration rules compared to other EU counterparts.

"Our goal is to find solutions that will meet the expectations of the British prime minister, while cementing the foundations on which the EU is based," said Tusk in the letter, cited by Reuters.

"Uncertainty about the future of the UK in the European Union is a destabilising factor. That is why we must find a way to answer the British concerns as quickly as possible."

Britain's growing dissent over immigration

Europe is going through its worst refugee crisis since World War II and over 1 million refugees, predominantly from Syria, are set to hit Europe's shores by 2016. The United Nations estimated another 1 million refugees will head to Europe next year as well.

In October, UK economist Robert Wood and his team Bank of America Merrill Lynch revealed that Britain is overwhelmingly anti-immigration and it could prompt a Brexit.

An IPSOS Mori poll cited by BAML recently found 50% of people say immigration among the most important issues facing Britain. This completely dwarfs other issues such as the economy (27%), unemployment (17%), and crime (13%).

"Current polls suggest that whether the British people would choose to leave the EU in a referendum whose date still needs to be decided is too close to call," said Wood and his team at BAML.

"In our view, many contingent factors are likely to play a role: any exacerbation of refugee issues could help 'pro-outs', while any strengthening in the European economic recovery may support 'pro-ins.'"

A YouGov poll cited by BAML shows that "Britons believe the country is more relaxed on immigration than other EU members." This probably explains why nearly a quarter of Britons polled in a Eurobarometer 2015 survey believe that the right of EU citizens to live in every member state of the EU is "a bad thing" - in comparison to an EU average of 9%.

It probably comes as no surprise then that a recent ComRes poll cited by BAML found that "78% of British voters felt it was important that David Cameron secured from the renegotiation limits on EU to UK migration flows."

The exacerbation of the Paris attacks

The spate of attacks in Paris in mid-November, which led to 130 people being killed and more than 300 people being injured, has only exacerbated the public's support for exiting the EU because of the unlikeliness of Britain being allowed to have greater immigration controls.

According to an opinion poll for The Independent on November 28, the majority of the 2,000 Britons surveyed are supporting a Brexit due to the migration crisis.

The Independent reported in the same story that the co-author of a new book on UKIP saidimmigration and identity issues are key to a lot of voters.

"Immigration is central to Euroscepticism in Britain," said Matthew Goodwin, Professor of Politics at Kent University. He found that voters who believe that immigrants impact negatively on the economy, welfare state, and culture are 16 times more likely to back "Brexit."

"The recent eruption of the refugee crisis and ongoing public concern over net migration have likely sharpened these anxieties even further, pushing Britain closer to the prospect of Brexit."