A $5.1 billion United States Postal Service credit card program for fuel purchases made by more than 400 mail-carrying contractors is “not manageable” and lacks needed protections against “fraud, waste and abuse,” according to a government watchdog.

The Postal Service has issued 12,000 Voyager credit cards used by contractors to buy 1.6 billions gallons of diesel fuel to carry the mail since 2005, the USPS inspector general said in a report made public Friday.

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