The chief executive of Goldman Sachs, Lloyd Blankfein, has suggested holding another referendum on Brexit.
Mr Blankfein tweeted: "Here in UK, lots of hand-wringing from CEOs over #Brexit... So much at stake, why not make sure consensus still there?"
The firm, which is known to have taken office space in Frankfurt, employs about 6,000 people in London.
Banks are particularly worried the UK will fail to strike an EU trade deal.
The banks fear that after Britain leaves the EU their businesses will lose "passporting rights", which allows them to sell financial services across borders.
Mr Blankfein's tweet went on to say: "Better sense of the tough and risky road ahead. Reluctant to say, but many wish for a confirming vote on a decision so monumental and irreversible.
Here in UK, lots of hand-wringing from CEOs over #Brexit. Better sense of the tough and risky road ahead. Reluctant to say, but many wish for a confirming vote on a decision so monumental and irreversible. So much at stake, why not make sure consensus still there?— Lloyd Blankfein (@lloydblankfein) November 16, 2017
Mr Blankfein's twitter account was barely used until recently.
Despite him signing up to the microblogging service in 2011 he only sent his first tweet in June - and since then has shared his thoughts in that way just 26 times.
Nevertheless, he has attracted 69,000 followers.
His previously most noticeable tweet - sent last month - was also Brexit-related: "Just left Frankfurt. Great meetings, great weather, really enjoyed it. Good, because I'll be spending a lot more time there. #Brexit".
That was seen as a hint that Frankfurt would become a key European base for the Wall Street giant post-Brexit.
Last month, the Wall Street bank said it had agreed to lease office space at a new building in Frankfurt giving it space for up to 1,000 staff.
That would be five times the current staff of 200 and see the Wall Street giant bolstering activities including trading, investment banking and asset management.
The bank is also thought to be looking at expanding its operation in Paris.
Mr Blankfein was in London attending a client event.
A spokesman for Goldman Sachs said the bank had nothing further to add to Mr Blankfein's comments.