David Rush allegedly exploited the agency’s secrecy rules, which restrict sensitive information to those with a “need to know”. Sources say he created a sham government contract and recruited two CIA colleagues to help run it, one of whom transferred millions of dollars into the invented programme.

By branding the project an ultrasecret “special access programme”, Mr Rush ensured his co-workers were barred from discussing it with other staff. Investigators do not yet know whether those colleagues were complicit or unwitting, NBS News reports.

The fictional programme purportedly involved contingency plans to keep the government functioning during a nuclear war or comparable emergency. Mr Rush is suspected of directing a defence contractor to buy large quantities of gold on the basis of the fraudulent contract. So far there is no indication he acted on behalf of a foreign power.

Arrested last month, Mr Rush faces one count of theft of public money, having allegedly filed false timesheets claiming Naval Reserve membership, though court documents suggest graver accusations. He has not entered a plea and remains in custody in Alexandria, Virginia, after a judge deemed him a flight risk.

He has left the CIA, and several senior officials have reportedly been placed on leave over the affair.