0Concerns about the European Union are at their highest level for 13 years in Britain ahead of a June 23 referendum on whether the country should stay in the bloc, but immigration and health are even more important to the public, a survey suggested on Friday.

Following Prime Minister David Cameron's announcement of the date of the in/out referendum after he renegotiated Britain's membership terms, the EU has shot up Britons' list of the most important matters facing the country, the monthly Economist/Ipsos Mori Issues Index found.

According to poll by British newspaper Telegraph, about 78 percent of Britons are in favor of U.K.'s EU exit. However, an analysis/poll by The Week say they came up with completely different figures, adding that only about 25 percent would vote yes on the Brexit referendum.

It said a fifth of the public mentioned the EU as amongst the most significant issues facing Britain, with 10 percent rating it as the most important. That was the highest level since 2003, when 10 new countries were allowed to join the bloc, the survey said.

However, the EU still trailed well behind immigration, mentioned by 44 percent of people, and the state-run National Health Service, mentioned by 38 percent, in the list of issues, while the economy was also still regarded as a more pressing concern.