Deutsche Bank has set up a “working group” to review whether to move parts of its British divisions to Germany if the UK leaves the EU.
The working group has been established, but it is “early days and no decisions have been made”, a spokesperson for the bank told the BBC.
Prime Minister David Cameron has promised a referendum on the UK’s EU membership by the end of 2017.
Deutsche Bank employs 9,000 people in the UK.
It is the first of the banks to publicly state that it is formally examining the potential fallout from the referendum, according to the Financial Times, which first reported the story.
Many businesses have urged the government to bring forward the referendum to end the prolonged wait.
James Bevan, chief investment officer of CCLA Investment Management, told the BBC’s Today programme that a review of the sort that Deutsche Bank was carrying out should be on the agenda of all major businesses in Europe.
“Every company that has business of a global nature, or indeed, particularly in Europe, is going to have to have at least a plan of what it will do, and any company that does not have a plan is absolutely remiss in managing its risks,” he said.
On Monday, British Chambers of Commerce director general John Longworth told the BBC that an in-out referendum should “take place as soon as is practical”.
Mr Longworth said that 55% of his members were in favour of a “reformed Europe”, and said the “in-out debate is more nuanced than a lot of people would have us believe”.
The chairman of construction equipment maker JCB also said on Monday that the UK should not fear an exit from the European Union.
“We are the fifth or sixth largest economy in the world. We could exist on our own – peacefully and sensibly,” Lord Bamford told BBC Midlands Today.