Up to 50,000 cars have not been traced in Mitsubishi's massive recall in Japan and some could have reached the UK as grey imports.
There are no official records of the cars which need to be traced to ensure they do not have technical faults.
Mitsubishi has been forced to check 620,000 vehicles - nearly all in the domestic market - with mechanical problems and most are in the Japanese market.
Over the last five years an estimated 50,000 grey imports have reached the UK direct from dealers in Japan. Many came to the UK through import companies which no longer exist.
David Miles, spokesman for Mitsubishi Motors UK, said: "We have been telling the factory for years to clamp down on dealers in Japan sending cars through on the grey market.
"Now the problem has come back to haunt us.
"We could ignore the problem because these vehicles were not official imports, but that would not do us or Mitsubishi Motors any good in terms of image.
"Instead we have to look at it as an opportunity to get these people into our showrooms and build a relationship with them."
A number of faults have been found on different Mitsubishi models in Japan which are specific to the domestic market. It is feared that some of these cars will have arrived here as grey imports.
##Space Wag--right##Problems include incorrectly fitted exhaust on Space Wagon (pictured right); leaking brake hose on old model Shogun and possible airbag inflation on Galant GDI and Lancer estate. The Evo IV and V have a possible yaw control problem related to the electronic suspension control unit.
Owners of grey market vehicles are being asked to take them to Mitsubishi dealers and those which require work will have the cost of labour and parts covered by the car maker.
Mr Miles said the main problem with grey imports is the catalytic converter which is made for use with higher grade gasoline used in Japan.