The entrepreneur who co-founded a UK-based money transfer business has told the BBC if he was doing it again, he wouldn't do it in London.
Fintech entrepreneur Taavet Hinrikus, co-founder of Transferwise, said Brexit was making it hard to source talent.
He said: "There is a lot uncertainty and uncertainty doesn't help business.
"So for starting up a new fintech company, [London] is not the best place any more."
Mr Hinrikus started Transferwise with fellow Estonian Kristo Kaarmann in 2011 and built it into a business with more than a million customers.
Speaking to BBC technology correspondent Rory Cellan-Jones, he said: "We came to London because of a great environment for entrepreneurship and because of a regulatory system that gives access to 500 million people in Europe.
"Today these things can't be taken for granted any more when it comes to getting other people to come to London. We don't know what it will be like in two years' time.
"We know that passporting of financial services is not going to happen any more, so it's the right thing today to consider whether you should do it in Amsterdam or Berlin or another city in Europe."
He was speaking at the government's International Fintech Conference in London, where Chancellor Philip Hammond told investors and entrepreneurs: "We need to continue to attract the brightest and the best from around the world to these shores - and we will."
Mr Hinrikus said: "Entrepreneurs are optimistic by nature. I am optimistic as I hope things will get figured out.
"Fix talent and everything else will fall into place. Make sure it remains easy to get foreigners to get to the UK and feel welcome here. If we get that sorted, it will go a long way."