The Central Bank has warned UK investment funds selling into Ireland not to market products there or in the rest of the EU after Brexit.
According to reports on Bloomberg, the Central Bank wrote to 53 UK mutual funds, known as UCITS.
It warned them they will lose the right to sell access to their funds in Ireland and the EU after the UK becomes a "third country" outside the bloc, the regulator said in an email response to questions.
Europe is seeking to ensure that it will continue to have oversight of asset managers, and regulators have warned that "letterbox entities", nominally based in Europe but managed from abroad, will not be tolerated.
The Central Bank has consistently said so-called brass-plate operations are not welcome in Ireland.
Firms authorised in Ireland here must be run from there, the regulator insists.
The 53 funds had all previously informed the Central Bank that they intended to market their units to Irish investors under EU rules, the regulator said.
The letter informed the funds they "will lose their right to market units in other member states of the EU including Ireland" when the UK exits the European Union.
Meanwhile, the Central Bank has written to the bosses of all regulated financial services firms reminding them of their legal obligations under its Fitness and Probity regime.
The regime was introduced in 2010 to ensure that individuals who work in regulated firms meet the highest standard of competence, integrity and honesty.
Derville Rowland, Director General of Financial Conduct at the bank, said the Fitness and Probity regime is central to its role as a gatekeeper for the financial system.
She said the regime ensures that the Central Bank can fully assess whether the most senior people working in the financial services industry are fit and proper.
"This is critical to the protection of the public interest and to ensuring that there is public trust and confidence in the financial system," Ms Rowland stated.
The central banker said that firms are the first line of responsibility to ensure that people working in key roles are fit and proper to hold those positions.
"This responsibility does not end when staff are hired to a position; firms must ensure that staff are fit and proper on an ongoing basis," she said.
She stressed that staff must be competent, but must also act with integrity at all times.
"Where we see evidence that firms are falling short in their obligations, we will take appropriate action, including removing individuals from those roles," the regulator warned.