Concerns have been raised regarding how the BREXIT vote will affect the planned merger of the London Stock Exchange and its German counterpart Deutsche Boerse.
Shareholders in the LSE are due to vote on the $27bn (£20bn) deal.
While both companies have said the outcome does not affect the logic of the deal, Germany’s regulator, Bafin, said the headquarters could not be in London, as had been planned.
“Without doubt… it is hard to imagine that the most important exchange venue in the eurozone would be steered from a headquarters outside the EU,” said Felix Hufeld, Bafin’s president.
As it stands, the deal is expected to be approved later today with German shareholders due to vote on it on July 12.
The companies hope to complete the deal in early 2017.