The FCA said it would continue to monitor the firm closely.
"T$3 his was an elaborate and sophisticated fraud, involving multiple parties around the world in different institutions, with a deliberate aim of deception", said EY in a statement to CNBC. The company's unravelling quickened earlier this week when it said that €1.9 billion previously reported as cash on its balance sheet probably doesn't exist.
"It is being continuously reviewed whether insolvency applications also have to be filed for subsidiaries of the Wirecard Group", the statement said. The company filed for insolvency Thursday.
Consumers were locked out of their accounts from Friday, when the Financial Conduct Authority (FCA) banned Wirecard Card Services, from carrying on any regulated activities or disposing of any funds or assets.
"We are maintaining pressure on the firm to resolve these issues which would allow it to operate under certain conditions", the FCA said.
Newcastle-based Wirecard Card Solutions Limited's licence was frozen after a major accounting scandal at its German parent company.
The European Union is investigating BaFin over the collapse of Wirecard, a rare measure that heaps embarrassment on Germany days before it is due to take over the EU's rotating presidency.
Wirecard is the first company to file for insolvency in the DAX 30, Germany's premier stock-market index.
KfW's subsidiary Ipex Bank granted the scandal-hit company a 100 million-euro credit line in September 2018.
The Financial Times revealed last week that Wirecard's auditors in EY's German office failed for at least three years to request crucial account information from a Singapore bank where Wirecard claimed it had up to €1bn in cash, a routine audit procedure that could have uncovered the fraud. There are no hedges to protect the lender from any losses, he added.