The French fund manager Carmignac is standing firm on a pledge to pass on investment research costs to investors once new EU rules come into force next year, despite a host of rivals reversing similar decisions in recent weeks.

The Paris-based firm also raised concerns that the approach taken by the majority of other fund managers — including BlackRock, Vanguard and JPMorgan Asset Management — to shoulder the costs could make it harder for newer investment managers to break into Europe.