Imposing its highest fine for client asset breaches, Britain’s financial regulator said there were “significant weaknesses” in Barclays’ systems and controls between November 2007 and January 2012 that put 16.5 billion pounds of client’s assets at risk.

The Financial Conduct Authority (FCA), which has tightened rules governing client asset protection since the collapse of Wall Street bank Lehman Brothers in 2008, said that customers risked incurring extra costs, lengthy delays or losing their assets if the bank had become insolvent.

“Barclays failed to apply the lessons from our previous enforcement actions, numerous industry-wide warnings and exposed its clients to unnecessary risk,” said Tracey McDermott, the head of enforcement and financial crime at the FCA.