The boss of America's largest bank has told Andy Burnham that higher taxes are driving firms out of Britain as he warned the new Prime Minister against a tax raid on the sector.
Jamie Dimon also reiterated his threats to scrap JP Morgan's London HQ as he warned Burnham of 'adverse consequences' to UK investment from left-wing policies.
The bank boss' comments came as Mr Burnham replaced Sir Keir Starmer as Prime Minister on Monday, and as he indicated a slew of new policies, there are growing fears that he will need to raise taxes to fund his spending spree.
One option available to Burnham would be to raise the bank levy or corporation tax surcharge, which Dimon said would be 'one more negative on that bucket of things you got to think about'.
Former Chancellor Rachel Reeves resisted pressure from left-wing MPs to introduce a levy on banks, which were originally imposed after the Government bailed out banks during the 2008 financial crisis.
The new Prime Minister and his more left-wing Cabinet could be more sympathetic to higher taxes on banks, but Dimon said it could have 'adverse consequences' for UK investment.
'I mean, it may sound great, 'tax the banks', but its $5billion that my shareholders paid on that extra tax,' Dimon told the Master Investor Podcast with Wilfred Frost.
'I just think things like that have adverse consequences.'
Dimon, who has led JP Morgan since 2006, also warned against changes to the current system, which sees banks pay a 28 per cent corporation tax compared to the standard 25 per cent.
'If you have an uncompetitive tax system, capital leaves your country,' he said.
'And if capital leaves your country, it goes to other countries. And you see that now. You see, what is it?
'How many companies have delisted from London in the last couple of years?
'I wouldn't want to see that if I was running a country'.
Dimon's comments come amid mounting concerns over the exodus of firms from the London stock market, as some choose to delist and others are taken over by foreign firms.
Analysis by City broker Peel Hunt shows the value of London-listed firms subject to bids was 27 times greater than the value of floats in the first half of the year.
Dimon also said that any changes to the tax regime could scupper JP Morgan's plans to build a new skyscraper in London.
He said he did not know what to do about the tower – which is expected to cost £3billion to build and be home to 12,000 employees – if Burnham raised taxes on banks.
Dimon warned: 'I would be very cautious if I was a government thinking that penalising any company out of the ordinary is a good thing for that country.'
The banking boss had previously warned that he would review JP Morgan's plans for the London HQ if the Government 'became hostile to banks again'.