Surely the bank that issues the cards could provide the information. The would require little or no use of Civil Service resources.

Simple solutions that the government won't every risk doing, but that would inspire faith:

♦  Eliminate future use of the credit cards.  Allow purchase of seats on government payment orders (no first class), $500/day travel allowance advances, receipts required, no guaranteed payment. 

♦  Community watchdog groups of say 5 should have final audit responsibility for the existing credit card debt, and should be able to bill the user for personal transactions. Pay them daily pay of say £75 each to do it; it will be the best money spent, and enforce transparency.

Consider using more of these citizen/watchdog committee for IPSA parliamentary expense resolutions, as well as local council/quango expenses/payroll/redundancy and gagging payments.