CAP Grey Book says grey importers do not have the benefit of a franchise to capitalise on the bumper new car sales and part-exchange that a new plate brings.
Writing in the latest edition, Grey Book editor Robert Hester said: 'While the rest of the market rides on the crest of a September wave, quite a few import dealers end up sitting around twiddling their thumbs because they didn't realise the wave was coming.
'Then they sit back and complain about how quiet things are. Forward-thinking importers make sure they have plenty of stock and, crucially, step up their marketing in order to capitalise on all this extra activity.'
Hester said it was also vitally important that the cars are prepared correctly.
'This means any remedial work must be completed, where necessary, and cosmetic body repairs and valeting are complete before the car is put out for sale,' he added. 'Unfortunately, some dealer forecourts reveal there are still some in the trade who continue to take short cuts in these areas, hoping to make a quick profit.'