One banker who responded to KPMG’s survey said: “There is a ‘doom loop’ where outflows cause investors the need to sell more, causing more underperformance.”

KPMG’s report found that bankers were unconvinced that the rule changes would improve the attractiveness of London.

The Big Four accountant surveyed dozens of senior bankers at 23 large US and European investment banks, including Barclays, Deutsche, HSBC, Goldman Sachs, and Citi.

One quoted in the report said: “Listing rule reform is rather ‘a nice to have’ than anything else.”

Aadam Brown at KPMG said: “The general consensus from leaders is that it is helpful, but it’s not going to materially change the issue of fund flows.”

The FCA’s plans include replacing London’s current premium and standard listings regime with a “single segment” system. Disclosure rules are also being relaxed to make them less onerous for companies.

KPMG’s report also uncovered concerns about the implications of relaxing London’s listing rules, with one respondent adding: “[W]hile we want to make the red tape a little easier, we need to be careful that we don’t jeopardise quality.”

Bankers said pay was a bigger issue for companies than red tape, with executives able to earn more if their companies were listed in the US.

London Stock Exchange chief Julia Hoggett has previously said the market was being “hampered” by advisers and asset managers blocking pay deals.

An FCA spokesman said: “We have been clear our proposals include a rebalancing of risk. We welcome feedback to make sure that we have the balance right.”

Elsewhere, the City received a boost on Friday after Kazakhstan’s national airline announced plans to list on the London Stock Exchange.

Air Astana on Friday said it will press ahead with plans to float in London and Kazakhstan as it continues to ride the post-pandemic rebound in travel.

The flagship carrier, which is owned by UK defence company BAE Systems and Kazakhstan’s sovereign wealth fund, hopes to raise $120m (£94m) from the initial public offering.