Japanese banks, including Nomura Holdings Inc. and Daiwa Capital Markets Europe Ltd., told U.K. City minister Simon Kirby and international trade minister Mark Garnier at a Dec. 1 meeting that they will relocate some operations from London within six months if "passporting" rights to the EU's single market following the U.K.'s exit from the bloc remain unclear, the Financial Times reported Dec. 16, citing two people "with knowledge of the meeting."

Japan's biggest banks have a small presence in continental Europe and so would be coming from behind were they forced to build a base in the EU, the FT noted.

Following the British referendum in June, some Japanese banks have already prepared for a potential move to the EU, with Mitsubishi UFJ Financial Group Inc. relocating staff from London to its Amsterdam office and Mizuho Bank Ltd. already having an office with its own passport in continental Europe, according to the report, while other banks are preparing to establish a larger footprint in the region as a base for expanded operations, if necessary.

However, the banks said they would prefer that most of their operations stay in the U.K. after it exits the EU, adding they remained committed to the country, the report added.