By Estelle Shirbon
LONDON (Reuters) - The economy trumps sovereignty and immigration as the key issue for Britons when they consider whether to vote to stay in or pull out of the European Union, data from an authoritative survey of public attitudes suggests.
Despite widespread and profound dissatisfaction with the EU, 60 percent of people think Britain should continue to be a member of the bloc, while only 30 percent believe it should leave, the British Social Attitudes survey has found.
The data was collected between July and November last year, through face-to-face interviews with a random, representative sample of 1,105 British adults.
While the data predates the deal that Prime Minister David Cameron reached on new EU membership terms for Britain, academics say the survey's random sampling method gives more accurate results than more up-to-date phone and internet polls.
The research found that 40 percent of people thought Britain would be worse off economically if it left the EU, while only 24 percent believed it would be better off, and this was the decisive factor in how they would cast their votes.
Since the survey was completed, the global economic outlook has deteriorated and although Britain is holding up well, the government has warned of a "dangerous cocktail" of threats to the economy.
The survey comes on the same day bosses at more than a third of Britain's biggest companies warned leaving the bloc would put the economy at risk.
Almost half of those surveyed said EU membership was undermining Britain's distinctive identity, citing grievances over a perceived threat to national sovereignty and over mass immigration from eastern European countries.
When the EU issue was broken down into a range of choices rather than a straight in-out dilemma, the survey found that two thirds of interviewees were eurosceptic, defined as wanting either to leave or to stay in a bloc with reduced powers.
But euroscepticism fueled by issues such as sovereignty or immigration translated into a desire to leave the bloc only for those people who also believed that the country would benefit economically from a "Brexit", the survey found.
John Curtice, Britain's foremost expert on electoral behavior, said the findings had important implications for those campaigning on both sides of the issue ahead of a referendum that will take place on June 23.
"The Leave campaign needs to win an economic argument about which, so far at least, voters are relatively dubious," he wrote in an academic paper analyzing the data released on Tuesday.
"The Remain campaign, meanwhile, needs to bolster its economic case ... while at the same time doing its best to argue that the renegotiations have at least assuaged some of the doubts and scepticism about the EU that many feel."
The referendum will offer voters a choice between staying in the bloc under the new terms negotiated by Cameron, or withdrawing altogether.
Cameron has pledged to put his "heart and soul" into the "in" campaign, but the ruling Conservative Party is split and the "out" camp received a boost on Sunday when popular London Mayor Boris Johnson announced he would push for a Brexit.
The British Social Attitudes Survey is conducted annually by NatCen Social Research, an independent, not-for-profit organization.
(Editing by Richard Balmforth)