EU officials want to make sure indices cannot be manipulated in the same way as Libor was by rogue bank traders and brokers.
But the Index Industry Association (IIA) argues that the vast majority of indices are far more transparent, and less vital to consumers and the economy.
“How could you even try to regulate this many indices equally? Just the data collected would amount to one terabyte every other day,” said IIA boss Rick Redding. “Regulators should focus on indices most open to manipulation.”
Otherwise, the extra burden could push indices to leave the EU or to close completely, he said.
The final rules are to be set out over the coming months.