LONDON (Reuters) - Britain's Financial Conduct Authority (FCA) has fined Coinbase business CB Payments Limited (CPBL) 3.5 million pounds ($4.5 million) for poor anti-money laundering controls, the watchdog's first enforcement action against a company involved in cryptoassets trading.

The FCA said on Thursday that CBPL, a gateway for customers to trade cryptoassets within the global Coinbase Group, voluntarily agreed in October 2020 to make improvements to its financial crime controls after a visit by the watchdog.

The agreement stipulated that CBPL could not accept new high-risk customers until the issues were addressed. The company, however, took on or provided e-money services to 13,416 such customers with nearly a third depositing $24.9 million, the FCA said.

This money was used to execute multiple cryptoasset transactions via other Coinbase entities, totalling about $226 million, the watchdog said, adding that repeated breaches of the voluntary agreement went undiscovered for almost two years.

"CBPL's controls had significant weaknesses and the FCA told it so, which is why the requirements were needed. CPBL, however, repeatedly breached those requirements," Therese Chambers, joint executive director of enforcement at the FCA, said on Thursday.

CBPL agreed to resolve the matter and qualified for a 30% discount on its fine, which would otherwise have been 5 million pounds.

"We welcome regulation and are dedicated to working proactively and closely with the most sophisticated financial regulators in the world, including the FCA, to ensure we offer the most compliant, trusted and secure platform for our customers," Coinbase said on Thursday.

($1 = 0.7762 pounds)