It would be against Britain's best interest to leave the European Union, an overwhelming majority of financial services executives have said.
According to an independent survey of 101 UK based chief executives and other senior officials by the lobby group CityUK, 84% wanted Britain to remain part of the EU.
Meanwhile 94% acknowledged the value of staying in the single market but they also thought the EU needed to make major reforms and cut regulation.
CityUK said 65% of those in its survey believe regulatory change to be one of the most important challenges to business; more than half viewed the volume of EU regulation as a major obstacle.
Eight out of 10 said staying in the EU was the best option for the competitiveness of the UK as a financial centre.
"Our research has shown that the benefits of EU membership are numerous for our respondents, not least in the gains we make from trade, increased competition, and by providing access to the world's largest market," said James Nixon, CityUK's chief economist.
A recent survey by the EEF, the UK's leading trade body for manufacturers, also showed strong support for the UK remaining in the EU.
According to the EEF, 85% of those from the industry polled said they want the country to retain its EU membership.
Prime Minister David Cameron has promised to renegotiate the UK's relationship with the EU and hold a referendum if re-elected in 2015.