Mitsubishi Motors and Toyota have warned 'grey' importers bringing cheap versions of their cars and pick-up trucks to Europe from Japan and Thailand they are prepared for court action to stop the estimated £300m-a-year business.

Mitsubishi has already forced one UK trader to return scores of cheap pick-ups to Thailand as part of an out-of-court settlement, and said it was confident European trademark law supported its position. It has also taken action in Ireland, while lawyers for both Japanese carmakers have written to scores of importers demanding they stop.