More than two-thirds of insurers, brokers and service providers working in London's international insurance market believe a Brexit would be bad for business.
Some 68.7 per cent of market practitioners surveyed believe a UK vote to leave the European Union would “hurt” or “severely damage” Lloyd's of London.
Meanwhile, 6.2 per cent said it would benefit Lloyd's and 25.1 per cent said it would have no impact.
For the study, commissioned by City financial PR consultancy Haggie Partners, researchers quizzed 259 individuals at the end of March.
Some 69.9 per cent of said they sell directly into the EU. Of the remainder, 58.2 per cent sell indirectly into the EU.
Of those surveyed, nearly 59 per cent believe the EU single market for insurance is the “best realistic international regulatory regime” for Lloyd's insurers.
Some 45.8 per cent chose the EU as the top priority for development as Lloyd's expands. Elsewhere, 23.7 per cent selected China, 16.2 per cent said Latin America, 10.7 per cent said India and 5.5 per cent said the Middle East.
“Lloyd’s centrally has clearly stated its preference for Britain to stay within the European Union, and this research shows that, from a business perspective at least, the vast majority of companies in the London market agree,” said Dr Adrian Leonard, who constructed the survey for Haggie Partners.
The survey also asked respondents about the replacement of the current Lloyd's chairman, who steps down next year.
Of those questioned, 58.1 per cent said the next chairman should be either a Lloyd's insider (24.1 per cent) or an insurance professional from outside Lloyd's (34 per cent). But 41.9 per cent said they would prefer a professional from another area of business.