The Bank of England (BofE) is demanding that lenders seek its approval before relocating UK jobs or operations, according to a report in the Financial Times.
The move comes after the BoE became concerned that European regulators are asking for more to move than is necessary for financial stability post-Brexit.
The BofE reportedly heard of several requests from the European Central Bank (ECB) that it considered excessive and beyond what is required from a supervisory perspective.
Any stays beyond the 90 days in any 180 day period will be dependent on the applicable visas and immigration rules for Spain."
Sources told the Financial Times that BoE governor Andrew Bailey had taken a personal interest in the issue.
This comes alongside the prospect of an estimated 500 UK citizens forced to leave Spain by its authorities for not having the correct residency paperwork.
Under the post-Brexit regulations British expats must register for residency by the 31 March deadline or they will be classed as illegal immigrants.
Expats must prove that they lived in Spain legally prior to 31 December 2020.
Third country nationals will only be allowed to visit Spain for no more than 90 days within a 180 day period in any country within the Schengen zone.
The British Embassy in Spain has said: "Any stays beyond the 90 days in any 180 day period will be dependent on the applicable visas and immigration rules for Spain. This may require applying for a visa and/or permit."