One of Germany's most senior banking regulators has warned London that it is likely to lose its role as "the gateway to Europe" for vital financial services.
Dr Andreas Dombret, executive board member for the German central bank, the Bundesbank, said that even if banking rules were "equivalent" between the UK and the rest of the European Union, that was "miles away from access to the single market".
Mr Dombret's comments were made at a private meeting of German businesses and banks organised by Boston Consulting Group in Frankfurt earlier this week.
They give a clear - and rare - insight into Germany's approach as Britain starts the process of leaving the European Union.
And that approach is hawkish.
"The current model of using London as a gateway to Europe is likely to end," Mr Dombret said at the closed-door event.
Mr Dombret made it clear that he did not support a "confrontational approach" to future relations between the UK's substantial financial services sector and the EU.
But he argued there was "intense uncertainty" about how the Brexit negotiations would progress and significant hurdles to overcome.
The Bundesbank executive, who is responsible for banking and financial supervision, said he was concerned that the trend towards internationally agreed standards was under pressure.
And that Britain might try to become the "Singapore of Europe" following Brexit, by cutting taxes and relaxing financial regulations to encourage banks and businesses to invest in the UK.
'Race to the bottom'
"Brexit fits into a certain trend we are seeing towards renationalisation," he said.
"I strongly believe that this negatively affects the well-being of us all.
"We should therefore invest all our efforts in containing these trends.
"This holds for the private sector as well as for supervisors and policymakers in the EU and the UK.
"Some voices are calling for deregulation after Brexit," he continued.
"One such example is the 'financial centre strategy' that is being discussed as a fallback option for the City of London.
"Parts of this recipe are low corporate taxes and loose financial regulation.
"We should not forget that strictly supervised and well-capitalised financial systems are the most successful ones in the long run.
"The EU will not engage in a regulatory race to the bottom."