Britain gets to vote on whether it will stay in the European Union by the end of 2017 and currently polls show that the pro and anti-EU camps are neck-and-neck.

Despite mass criticism and protests from campaigners, human rights groups and left-wing media over the British government's handling of the worst refugee crisis since World War II, the latest report from Bank of America Merrill Lynch shows that Britons would actually vote to leave immediately if immigration was not reduced or more tightly controlled.

In other words, Prime Minister David Cameron did exactly what a majority of Britain wants by saying that the country will only accept around 20,000 refugees over the next few years — a drop in the ocean compared Germany's pledge to take in 800,000 refugees this year alone.

UK economist Robert Wood and his team at BAML revealed that immigration is the number issue for voters and Britain is the least supportive of taking in refugees. 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%).

In fact, if Cameron is unable to renegotiate the rules around immigration as part of a role as an EU member, it is more than likely to push voters to support a Brexit.

"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.'"

The report lists a number of pretty devastating charts and statistics that all point towards Britain's stance regarding immigration. Take a look at this chart:

Other stats show that Britons are overwhelmingly negative when it comes to Freedom of Movement – the automatic ability for any EU citizen to go and live in another EU member state.

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."

In other words, Brits really are not happy about current immigration levels, so the refugee crisis could push the UK out of the EU.

Just look at this table and how many people are gunning for migration limits:

Wood and his team at BAML shot a warning about how it's nearly impossible to call an outcome of the EU referendum due to the uncertainty over Cameron's ability to seal this so-called new deal with the EU.

"We believe PM Cameron will struggle to achieve the headline-grabbing changes that could put the referendum result beyond doubt," said the BAML note. "Do we think he could achieve a facesaving deal? Yes. Are important but arcane changes likely? We think yes. Will he be able to restrict migration or allow discrimination by nationality? No. Could there be a change to the totemic 'ever closer union' goal from the Treaty of Rome? Possibly, but it is far from certain."

This issue will not go away.

The more migrants arrive in Britain, the more it drives anti-EU sentiment. Cameron wants limits on migrants but EU membership rules allow unlimited migration within Europe's borders. So Cameron wants to negotiate the terms of Britain's EU membership to limit migration if Britain stays in. But the longer he waits to hold the EU vote, the more migrants arrive, and the greater the groundswell against the EU within Britain grows.

A huge influx of refugees this year from Syria and other Middle Eastern and African nations is set to continue, with another 700,000 migrants and refugees in 2016 – so the arguments are likely to keep going.

It seems that the only way Britain can remain in the EU right now is if Cameron secures tighter immigration rules and immediately calls a referendum straight after.