European regulators have warned banks working on post-Brexit plans that they will “need to have substance locally” to serve European clients.
The European Central Bank said some of the proposals it has reviewed are inadequate and risk creating “empty shells”.
Many banks currently gain access to the European market through UK offices.
They have said they are working on contingency plans, adding space in cities such as Frankfurt and Dublin.
The Bank of England has said it is braced for the potential loss of 75,000 finance jobs following Britain’s departure from the European Union.
But with details of the split unclear, some banks have held out hope that the break would not be so disruptive.
The chief executive of Barclays, Jess Staley, has said he hopes to avoid significant changes to the current set-up.
Many of the announcements of changes have also been less dramatic than expected.
JP Morgan said it might have to move 4,000 jobs, but since the referendum has cut that number to around 1,000.
The Swiss bank, UBS, said it may move as few as 250 jobs after initially planning to relocate as many as 1,000.
The ECB said it is looking for bigger changes than some firms currently contemplate in their relocation plans.
The ECB said finance firms must have local trading abilities and local risk committees, among other requirements.
“ECB Banking Supervision appreciates the progress banks have made in their Brexit preparations,” it said in its autumn newsletter.
“However, some elements in a number of banks’ plans do not fully meet the ECB’s expectations and requirements of banks operating in the euro area.”