The Financial Conduct Authority (FCA) in the UK has fined custodian Bank of New York Mellon (BNY Mellon) £126m (€175.4m) for failing to follow rules meant to keep client money safe over a six-year period.

The fine applied to the London Branch (BNYLB) and Bank of New York Mellon International (BNYMIL). The Bank of New York Mellon Group, to which the firms belong, is the world’s largest global custody bank by safe custody assets, the regulator said.

Georgina Philippou, acting director of enforcement and market oversight at the FCA, said: “The firms’ failure to comply with our rules including their failure to adequately record, reconcile and protect safe custody assets was particularly serious given the systemically important nature of the firms and the fact that safeguarding assets is core to their business.”

If the subsidiaries had become insolvent, the total value of safe custody assets at risk would have been significant, she said.

Philippou noted that the severity of the breach was compounded by taking place over a period of “considerable” market stress.

During the period of the rule breaches, BNYMLB and BNYMIL — the third and eighth biggest custody banks in the UK respectively — held up to £1.3trln and £236bn in safe custody assets, the regulator said.

“As a result of this, the firms are systemically important to the UK market,” Philippou said.

In a statement, BNY Mellon noted that its fine had been lowered due to its “cooperative efforts”, and that the sum would be met from pre-existing legal reserves.

”Importantly, BNY Mellon remained financially robust throughout the relevant period and, as indicated by the FCA in its Final Notice, no clients suffered any loss as a result of the issues identified.”

The firm said it regretted that it had failed to meet its own or the FCA’s standards, and that it had conducted an independent review and amended its policies.

BNY Mellon was one of six appointed to a national custodian framework agreement launched by a number of UK local government pension schemes in 2013.

The FCA said the firms had failed to comply with its Client Assets Sourcebook (Custody Rules, or CASS).

The rules are meant to protect safe custody assets if a firm becomes insolvent, making sure the assets can be given back to clients as quickly and easily as possible, the regulator said.

Instead of keeping entity-specific record and accounts for the client safe custody assets they held, as required, the FCA said the firms used global platforms to manage the money, which did not record with which BNY Mellon Group entity clients had contracted.

The firms also failed to stop safe custody assets being commingled with firm assets from 13 proprietary accounts, and occasionally used safe custody assets held in omnibus account to settle other clients’ deals without getting proper permission from all parties.

“Other firms with responsibility for client assets should take this as a further warning that there is no excuse for failing to safeguard client assets and to ensure their own processes comply with our rules,” Philippou said.