Sky News reports that Jamie Dimon met the Chancellor in Downing Street on Thursday, warning about the "cliff-edge" disruption to financial markets.
Dimon previously stated that Brexit could force him to move up to 4,000 jobs out of the UK, although no decision has yet been announced.
Last month, Anthony Browne, chief executive of the BBA, warned that banks are already planning to relocate from Britain as a result of the Brexit vote.
Browne puts this largely down to the expectation that the UK will lose its passporting rights post-Brexit. He describes a financial services market that is underpinned by the passporting system enshrined in EU legislation, which allows banks based in the UK to sell services to customers in Europe, and banks based in Europe to sell services to customers in the UK.
The IFS and Treasury Committee have also raised concerns over the effects of losing full access to the Single Market in financial services.
