A so-called "hard" separation of the UK from the European Union would prompt Goldman Sachs to shift 2,000 highly paid staff out of London.
The loss of Britain's prized preferential access to the single market would lead the Wall Street stalwart to move one in three of its employees to rival financial hubs across Europe, The Sunday Times reported.
At the Conservative party conference, Prime Minister Theresa May indicated single market access would be a target during the Brexit negotiations — but the government will not allow the freedom of movement required to secure it.
Goldman Sachs said: "We have not taken any decisions as to what our eventual response [to Brexit] will be, despite media speculation to the contrary."
Earlier this month, chancellor Philip Hammond visited New York to reassure top Wall Street bankers that protecting access to Europe for financial services firms based in London was a pressing concern not only for UK businesses but also European ones that rely on London’s status as global financial hub.
However, the bank bosses told him that they would be forced to move jobs out of London unless the UK secures preferential access to the single market.
Jamie Dimon, the chief executive of JP Morgan, said in the US over the weekend that Brexit would create "years of uncertainty" for banks which have large operations in London, the Financial Times reported.
Meanwhile, the chief executive of Morgan Stanley, James Gorman, added that the bank was looking at whether it needed a new headquarters in the Eurozone, or to move some compliance and back-office teams there.
The head of the the Confederation of British Industry (CBI) and the manufacturers' organisation EEF yesterday published an open letter to the government urging it to avoid a "hard Brexit".
The business lobby groups called on the government to "give certainty to business by immediately ruling this option out under any circumstances".