Britons gave their views about Europe to the Observer in a wide-ranging survey | Peter Macdiarmid/Getty Images Immigration tops list of UK worries, Brexit in top three Britons on fence ahead of June Brexit referendum.

Britons see immigration as the most important issue affecting the U.K. ahead of this summer's EU referendum, according to a poll in the Observer Sunday on British attitudes towards Europe.

While 53 percent ranked immigration in the top three most important issues affecting the country, just 31 percent of the population identified Britain’s membership of the EU in that top bracket. Health and the National Health Service ranked above EU membership on issues Britons are most concerned about.

Nearly 50 percent of respondents to the poll said they would cast their vote based on immigration and its perceived problems.

The poll was conducted prior to David Cameron sealing a deal with EU leaders at a summit last month, and the announcement of June 23 for the referendum vote.

The knife-edge on which the U.K. sits was evident in the question about referendum voting intentions: 40 percent of respondents say they would vote to remain in the EU, 41 percent would vote to leave, and a crucial 19 percent are still undecided.

The survey contained some evidence that there may be momentum towards leaving the EU. Some 38 percent of those polled said they had changed their minds on a potential Brexit in the last six months.

This period included the Paris terror attacks, a continuation of the migrant crisis, and the mass sexual assaults in Cologne on New Year's Eve.

While the poll found Britons were relaxed about the impact of Brexit on their personal finances, with 38 percent believing they'd be better off after leaving, 54 percent agreed the country should be part of a European trading bloc, with just 14 percent dissenting. The eurozone crisis has resonated in Britain, with 68 percent of those polled admitting that they question the country's stability.

Despite these economic concerns, Angela Merkel, at 79 percent, was the landslide winner of a question asking who was the most influential European leader. David Cameron was second with a meager eight percent, and Jean-Claude Juncker finished won five percent. Just 8 percent of Tory respondents called him the most powerful, in line with the percentage of total respondents with that view.



On a lighter note, Spain was the European country most U.K. residents would like to live in, apart from their own. The Iberian nation polled 15 percent, with Italy and France next with 12 percent and 10 percent, respectively. Romania was the runaway loser in this category, with 25 percent of respondents saying it would be the country in which they'd least like to reside.

The survey was conducted by Opinium Research among a sample of 1,033 U.K. adults aged 18 and over. Interviews were conducted using an online panel and results weighted to be demographically representative of the total U.K. adult population.