Senior EU officials are reviewing how they grant market access to overseas financial firms, which may make it harder for City firms to operate post-Brexit.
The Financial Times reports officials at the European Commission are considering equivalence rules which give limited access rights to countries outside the EU where regulations are broadly similar to EU rules.
One official told the newspaper equivalence “is not automatic and is not a right.”
Invest Europe, which represents private equity and venture capital firms, questions why clear processes set out in EU legislation for passporting rights are not being followed.
Chief executive Michael Collins says: “Firms across the world are left wondering what they should expect in terms of access to the EU market.”
University of Dundee research fellow in finance, banking and regulation Richard Reid says: “Even before the Brexit vote, the last financial crisis had fostered an environment of more intrusive regulation.
"Now, with some in the UK arguing that perhaps one way forward for its financial services industry is to benefit from being freed from unwarranted EU legislation, it may be unrealistic to think that gaining EU equivalence recognition will be straightforward.”