The UK should stay in the EU but David Cameron should seek to gain key concessions from Brussels in a bid to forge a "better, more thoughtful Europe", according to TheCityUK.
The campaign group, which is funded by and represents finance and professional services firms in Britain, outlined 25 proposals for reform in the EU.
The organisation stressed the proposals are "not about 'more Europe' or 'less Europe', but about creating a 'better, more thoughtful Europe'."
The group wants, among other things, better regulation, a "European agenda for jobs" and "fair and equal treatment" of all member states ahead of a promised referendum on the UK's membership of the union.
"Fact not fiction should inform the EU reform agenda. The evidence we've gathered from the financial and related professional services industry shows that continued membership of the EU is vital for UK competitiveness, but a lot needs to be change if the EU is to better serve the interests of its 500 million people," said Sir Gerry Grimstone, chairman of TheCityUK.
"The City is Europe's financial capital and our members, representing many different countries, want practical change that can be delivered quickly, promote economic growth, bolster global trade and investment, and secure Europe's competitive position in the world. Let's get on with it."
The report comes after Sajid Javid, the business secretary, criticised one of the UK's top business bodies for calling for Britain to stay within the 28-member bloc "no matter what".
The top Tory, speaking at the CBI (Confederation of British Industry) president's dinner in London, said the group's position threatened to undermine Cameron's plan to win major reforms from the Brussels.
"You know how negotiation works. You wouldn't dream of sitting down at the start of a merger or acquisition and, like a poker player showing his hand to the table, announce exactly what terms you were prepared to accept," the minister said on 29 June.
He added that "it doesn't work in the boardroom and it won't work in Brussels".
"Make no mistake, the reforms we seek are the reforms your members need. An expanding market that liberalises new sectors will benefit British entrepreneurs," Javid said.
"An EU open to trade, concluding ambitious deals with America, China and Japan will benefit all British businesses and consumers. And, as the prime minister has said before, this renegotiation will not just benefit Britain. It will benefit the whole of the EU too."
The remarks come after Sir Mike Rake, the president of the CBI, urged companies to "speak out early" in favour of the UK remaining inside the 28-member bloc.