More than one hundred City leaders have thrown their weight behind leaving the European Union, arguing that the euro and red tape threatens to hold back UK firms.
City grandees said that when the UK joined the European Economic Community in 1975 it had benefited for many years, but now the European single currency and increased regulation now presented problems that "may prove insurmountable".
A letter signed by 110 business leaders appears in today's Evening Standard newspaper backing the Vote Leave campaign ahead of the EU referendum vote on June 23.
The letter is signed by veteran City figures such as fund manager chairman Paul Marshall of Marshall Wace, Pizza Express entrepreneur Luke Johnson and founder of buyout firm Better Capital Jon Moulton.
The leaders said: "The EU is now shackled to the euro, a project doing damage to the social and economic fabric of member countries, including high youth unemployment.
"Many of us worry that the eurozone's problems may prove insurmountable.
"Meanwhile there is scant evidence that the EU will foster or support the kind of innovation which is essential if Europeans are to compete with the rest of the world.
"Specifically, we worry that the EU's approach to regulation now poses a genuine threat to our financial services industry and to the competitiveness of the City of London."
The move follows a letter sent business leaders to the Times in February who want the UK to remain inside the EU.
That letter - backed by bosses at BT, Marks & Spencer and Vodafone - said leaving the EU would threaten jobs and put the UK's economy at risk.