Investment in Britain's energy sector could suffer if the country left the European Union, the chief executive of BP Bob Dudley said on Wednesday.
"Being outside the EU would be worse for the country as many of the rules would still apply and Britain would be in danger of losing influence on the world stage," he told the BBC.
"I think many of the trade regulations would still apply even if Britain were outside," he said.
"There are lots of technical tax reasons, trade flows, regulation, that would make it better for our business and the energy business in general, the oil and gas business, (if Britain) were a part of Europe."
Prime Minister David Cameron is renegotiating his country's membership of the 28-member trading bloc and could reach a deal with EU partners at a summit next month, paving the way for a public vote as soon as June.
Dudley said he backed Cameron's efforts to make the bloc more competitive.
"I think Europe can be more competitive," he said, adding "I think Europe needs Britain."
Several large British businesses have spoken out in favour of the EU, often due to tariff-less trade which they benefit from, although many smaller firms have criticised the bloc for imposing what they argue are costly regulations.
(Reporting by Stephen Addison; editing by Costas Pitas)