The sharp response from Fratto and other industry figures came as Trump was rolling out his economic agenda at the second day of the Republican National Convention.
Wall Street's objections signalled a growing breach in a party that has enjoyed a steady stream of campaign contributions from banks, hedge fund and private equity executives over the last 15 years.
Perhaps the most telling evidence of the alienation is Wall Street's near-absence from the festivities this week.
Major banks that sponsored GOP nominee Mitt Romney's coronation in Tampa four years ago are missing. Some of the party's wealthiest donors, such as hedge fund billionaire Paul Singer, are pointedly staying away.
The distancing comes after Trump's swipes at Wall Street and positions on free trade and immigration have alarmed finance industry leaders, said Howard Schweitzer, who served as a senior Treasury Department official under Barack Obama and George W. Bush.
"People assume because he resides in New York that he's cosy with Wall Street, and he just isn't," Schweitzer added. "They aren't excited about him. They don't know him and they don't like his policies."
In 2012, the financial services industry lavished money on Romney, a private equity chieftain, with the largest share of contributions to his campaign coming from employees of Goldman Sachs, Bank of America, Morgan Stanley, JP Morgan Chase, Wells Fargo and Credit Suisse, according to the Center for Responsive Politics. The securities and investment sector alone poured US$37 million more into a super PAC backing the GOP nominee.
The response to Trump, by comparison, has been notably muted - as of May 31, employees of banks, securities firms and insurance companies had donated just US$127,041 to his campaign, according to the centre.
Trump allies note that the current figures do not reflect the campaign's biggest fundraising haul, when it raised US$52m last month in conjunction with the Republican National Committee.
Steven Mnuchin, a hedge fund manager with strong ties to Wall Street, serves as Trump's finance committee chairman, and said the media has promoted an inaccurate image of Trump's posture toward the industry.
"Donald is not critical of Wall Street," he said. "He is critical of Hillary Clinton for accepting large speaking fees from Wall Street. That's different from him being critical of the financial services industry."
However, Trump has repeatedly bashed hedge-fund managers for the tax rate they pay, saying last year that they are "getting away with murder".
Trump campaign chairman Paul Manafort noted that the party platform would call for the reinstatement of the Glass-Steagall Act "so that we create barriers between what the big banks can do and try to avoid some of the crisis that led to 2008".
Glass-Steagall, a Depression-era measure that curtailed major banks from investment activities, was repealed by a 1999 law signed by President Bill Clinton. Its restoration has long been a rallying cry for consumer advocates and politicians on the left, who blame the deregulation for setting the stage for the 2008 financial crisis.
By pushing for its renewal, the Republican party now finds itself aligned with liberals such as Senator Bernie Sanders, who succeeded in getting a similar measure into the Democratic party platform this year. Hillary Clinton has been opposed to bringing the law back.
At the US Chamber of Commerce, Tom Quaadman, a senior vice-president, wrote that restoring the regulations would cause Main Street businesses "to take unanticipated measures, scaling back investing".
The controversy could drive more Wall Street funds to Clinton, who already has the backing of industry leaders such as former Goldman Sachs chief and Treasury Secretary Hank Paulson.
That's not to say Wall Street will abandon the GOP: the industry still has a strong bulwark among Republicans in Congress, particularly allies such as House Speaker Paul Ryan.
But there is a striking dearth of industry events taking place this week in Cleveland - and a diminished corps of lobbyists working the crowd.
