Mr. Romney picked a precarious time to visit London’s financial community. British, European and American banks here are under close scrutiny from regulators on both sides of the ocean for their attempts to manipulate key interest rates.

So far Barclays, Britain’s third largest bank, has been at the scandal’s forefront, and the bank’s former chief executive, Robert E. Diamond Jr., withdrew his name from Thursday’s event after he was forced to resign from the bank. Patrick Durkin, a senior lobbyist for Barclays in Washington who has raised more than $1 million for Mr. Romney, remained a co-chairman.

The rate-rigging scandal has set off a vocal anti-banker backlash here, with everyone from the governor of the central bank to David Cameron, Britain’s conservative prime minister, weighing in on how badly bankers have behaved. Eleven members of Parliament even recently signed a resolution that named Mr. Romney and called for Barclays executives to “cease fund-raising for political candidates.”

Accusations that HSBC, Europe’s largest bank, which is also headquartered in London, engaged in money laundering practices and the fact that most of J. P. Morgan’s derivatives trading losses originated here have not helped the city’s financial reputation either.

But the malaise is broader than that. The euro zone debt crisis and a lingering recession in Britain have sharply curbed core banking operations like lending, trading and deal-making, and many companies with large investment-banking operations here, like Deutsche Bank, are contemplating deeper job cuts as profits sag.

Nevertheless, even though this year should see a significant bonus reduction for most in the banking world, Mr. Romney’s visit has prompted many to reach for their checkbooks. Indeed, while many bankers here accept that banker conduct must improve, they worry that the push for more regulation and higher taxes — not to mention the public attacks on their profession, both here and in the United States — has gone too far.