Over-supply in the used car market has allowed car traders to cherry-pick the best models, which need the least amount of work before going on to the forecourt.
This works against companies which have skimped on the expense of repairing vehicles, so that the work is noticeable to the experienced buyer, either deterring them from bidding for the vehicle at all or forcing down its value.
John Ellis, head of business development for bodyshop network ABS, said: 'This is a new development that has come to light during the past few months.
'If a fleet manager has a quality car that is being defleeted but has dents too large to repair, some will often push them in the direction of their local 'under-the-arches' bodyshop to get a job done. The work is designed to get the car in A1 condition long enough to get it through the auction.
'But we have seen some of these cars coming into our bodyshops recently for re-repairs. Cars are in such plentiful condition and good motor traders can spot the signs of a rushed repair.'
Sellers are affected in two ways, firstly with executive cars, where vehicles must be in the best possible condition and are inspected closely during sales.
The second area covers mainstream cars, such as Ford Mondeos and Vauxhall Vectras, where any signs of rushed repairs have an exaggerated effect on residual values.
Ellis said: 'Sending vehicles to market with a rush repair is having a detrimental affect on residual values.'