The EU is planning to introduce new rules for foreign banks in a move which could add to financial firms' Brexit worries.

The European Commission is set to unveil proposals tomorrow which are similar to the "intermediate holding company" rules introduced in the US, according to The Financial Times.

Investment banks from outside the EU would be required to hold additional capital and meet tougher liquidity requirements to safeguard against future financial shocks.

When the US originally introduced these measures it was accused of protectionism by European officials.

This is likely to make the cost of doing business higher for financial firms who remain in the UK following Brexit - although the financial paper reports that officials say these rules were not developed with Brexit in mind.

Europe's move could be part of a broader fragmentation and localisation of financial rules.

It comes at a time when EU/US relations have been strained by the US Department of Justice's seeking of a $14bn payout from Deutsche Bank relating to its packaging and selling of mortgage-backed securities. It could lead to a further escalation in trans-Atlantic tensions at a time when Donald Trump's election victory is already creating uncertainty.