Nigel Green of deVere Group urged Chancellor John Healey to dismiss union leaders lobbying for a new windfall tax on bank profits to help fund household energy bills.

He said: “Every finance minister eventually learns the same lesson the hard way. Capital doesn’t sit still and wait to be taxed. It moves to wherever the environment is friendliest, and it moves fast.

“Big profit numbers make an easy talking point for anyone pushing a windfall tax. What gets left out is that financial and professional services already deliver a record share of the tax take that funds the schools, hospitals and energy support Healey wants to protect.”

On top of standard corporation tax at 25%, lenders pay an additional 3% surcharge plus a separate levy on their balance sheets, both introduced in the aftermath of the 2008 crisis and never fully unwound.

“Punishing the sector that pays for those things is self-defeating. Nobody is asking for sympathy for an industry that’s profitable again. But Britain’s banks are already taxed well above the rate applied to most other sectors. Layering a windfall charge on top of that only deepens an imbalance that already exists.”

Mr Green’s remarks came after JPMorgan Chase CEO Jamie Dimon privately urged the Chancellor against making the UK a more hostile place for banks to operate, explaining that an uncompetitive tax system would drive jobs away, pointing to a decline in finance roles in New York.

The deVere boss added: “London should be paying very close attention to what’s happening across the Atlantic. A city can price itself out of the industry that built its skyline, and once those jobs relocate, they rarely come back on demand.

“Global banks don’t make 30-year property and headcount decisions based on hope. They make them based on whether a government looks predictable. Every signal of a harsher regime pushes that decision further from London and closer to Frankfurt, Dublin or New York.

“Growth comes from stability, not from raiding the sector that’s finally performing. Healey has a genuine chance to back the industry that funds the country. Reaching for a windfall tax instead would be a costly mistake dressed up as a quick win.”