The boss of JP Morgan, Jamie Dimon, has warned he could scrap plans to build a new £3bn UK headquarters in London if Keir Starmer is replaced by a new Labour prime minister who is hostile to banks.

JP Morgan revealed plans last November to build the tower in Canary Wharf, hours after lenders were spared tax hikes in Rachel Reeves’s autumn budget following strong lobbying by the banking sector.

Dimon said the US bank could look past the current political instability around Starmer’s future in No 10, which has roiled bond markets and sent domestic bank shares plunging.

However, he warned that plans to build the bank’s new HQ – which will house more than half of its 23,000 UK staff – could be reversed if a new leader were to target lenders.

He told Bloomberg TV during an interview in Paris on Tuesday that construction plans would be threatened “not [by] political instability, but if they become hostile to banks again”.

“I’ve always objected to the fact … we paid probably $10bn in extra taxes by now,” he added. “I don’t think that’s right or fair. If that happens too much we will reconsider.”

It is understood that Dimon was referring to the UK’s decision to target banks with two sector-specific taxes as a result of the 2008 financial crisis: the bank surcharge, which is a tax on bank profits, and the bank levy, which applies to certain parts of lenders’ UK balance sheets.

Dimon has publicly praised Starmer and Reeves in the past, and said on Tuesday that Starmer was a “smart guy”. However, JP Morgan stressed in November that the Canary Wharf tower plan would depend on “a continuing positive business environment in the UK”.

Questions were recently raised about the financial inducements the company has sought from the UK government to build the skyscraper. JP Morgan has requested a discount on its business rates, according to documents produced by Tower Hamlets council, despite having reported a net income of $57bn (£43bn) in 2025.

The current political turmoil has ruffled feathers in other corners of the City, with one investment banking source telling the Guardian that stock market flotations “could be derailed” by a leadership fight.

“If you’re planning for an IPO, for example, you need stability in the markets … There’s been talk of a number of IPOs coming down the track in the UK, and that gets derailed in situations like this.”

They added that there had been “quite positive signals from the City” about Reeves’ plans to generate growth, “so for anything to be derailed at this point would be damaging”.

“The worst thing at the moment would be going through another messy leadership race,” the source said, adding that “we don’t want to see what we experienced with the previous government” – a reference to the Conservative party’s rotating cast of prime ministers.