The ECGD, the official export credit insurer, has written off the money, as it is not believed possible to reclaim it, and will take no further action. It is one of the biggest write-offs of public money.
The ECGD's official response to a Public Accounts Committee hearing into the affair last year will be published this week.
Robert Sheldon, committee chairman, said yesterday that the overpayment had been a very serious matter and he could not rule out further inquiries if the ECGD's response was inadequate.
The ECGD's offices in London and Cardiff had been operating to different guidelines over how much to pay companies when export contracts turned sour.
Since 1975 the ECGD had overpaid by at least £83m, though Mr Sheldon said the total could have been much higher, as the relevant paperwork was missing. The discrepancy was uncovered in 1992 when the ECGD was being computerised.
Brian Willott, ECGD chief executive, has instituted a review of procedures. But the minutes of his response to the PAC's criticism will show no case for serious reprimand.
The Cardiff operation is now owned by NCM Credit Insurance. Mr Willott said: "All those responsible are deceased, retired or no longer employed by the ECGD." Two officials in the London office have been reprimanded, but remain in their positions. Mr Willott said: "After very careful consideration I have concluded that this is the extent of the disciplinary action that is appropriate."
Mr Sheldon said: "We are keeping a close watch on this to see what action the ECGD is taking, but I would prefer to see the minutes before commenting further."
The department yesterday announced that it insured more new business last year than it had for a decade. Total new business rose 8 per cent to £4.1bn and the department made a net contribution to the Treasury for the first time in many years.
Mr Willott said cover for defence exports accounted for close to half of new guarantees compared with an average of 20 per cent in normal years. On the financial crisis in Mexico, he said the ECGD had not been affected but was keeping a very close watch on developments.